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germanium in nature. Germanium is a rare and useful semimetal.




Please note that germanium is taken by us in any quantity and form, incl. the form of scrap. You can sell germanium by calling the telephone number in Moscow indicated above.

Germanium is a brittle, silvery-white semimetal discovered in 1886. This mineral is not found in its pure form. It is found in silicates, iron and sulfide ores. Some of its compounds are toxic. Germanium was widely used in the electrical industry, where its semiconductor properties came in handy. It is indispensable in the production of infrared and fiber optics.

What are the properties of germanium

This mineral has a melting point of 938.25 degrees Celsius. The indicators of its heat capacity still cannot be explained by scientists, which makes it indispensable in many areas. Germanium has the ability to increase its density when melted. It has excellent electrical properties, which makes it an excellent indirect-gap semiconductor.

If we talk about the chemical properties of this semimetal, it should be noted that it is resistant to acids and alkalis, water and air. Germanium dissolves in a solution of hydrogen peroxide and aqua regia.

mining germanium

Now a limited amount of this semi-metal is mined. Its deposits are much smaller compared to those of bismuth, antimony, and silver.

Due to the fact that the proportion of the content of this mineral in the earth's crust is quite small, it forms its own minerals due to the introduction of other metals into the crystal lattices. The highest content of germanium is observed in sphalerite, pyrargyrite, sulfanite, in non-ferrous and iron ores. It occurs, but much less frequently, in oil and coal deposits.

Use of germanium

Despite the fact that germanium was discovered quite a long time ago, it began to be used in industry about 80 years ago. Semi-metal was first used in military production for the manufacture of some electronic devices. In this case, it found use as diodes. Now the situation has changed somewhat.

The most popular areas of application of germanium include:

  • optics production. Semimetal has become indispensable in the manufacture of optical elements, which include optical windows of sensors, prisms, and lenses. Here, the transparency properties of germanium in the infrared region came in handy. Semimetal is used in the production of optics for thermal imaging cameras, fire systems, night vision devices;
  • production of radio electronics. In this area, semi-metal was used in the manufacture of diodes and transistors. However, in the 1970s, germanium devices were replaced by silicon ones, since silicon made it possible to significantly improve the technical and operational characteristics of manufactured products. Increased resistance to temperature effects. In addition, germanium devices emitted a lot of noise during operation.

The current situation with Germany

Currently, semimetal is used in the production of microwave devices. Telleride germanium has proven itself as a thermoelectric material. Germanium prices are now quite high. One kilogram of metallic germanium costs $1,200.

Buying Germany

Silver gray germanium is rare. The brittle semimetal is distinguished by its semiconductor properties and is widely used to create modern electrical appliances. It is also used to create high-precision optical instruments and radio equipment. Germanium is of great value both in the form of a pure metal and in the form of dioxide.

The Goldform company specializes in the purchase of germanium, various scrap metal, and radio components. We offer assistance with the assessment of the material, with transportation. You can mail germanium and get your money back in full.

Germanium (from the Latin Germanium), designated "Ge", an element of the IVth group of the periodic table of chemical elements of Dmitry Ivanovich Mendeleev; element number 32, atomic mass is 72.59. Germanium is a gray-white solid with a metallic luster. Although the color of germanium is a rather relative concept, it all depends on the surface treatment of the material. Sometimes it can be gray as steel, sometimes silvery, and sometimes completely black. Outwardly, germanium is quite close to silicon. These elements are not only similar to each other, but also have largely the same semiconductor properties. Their essential difference is the fact that germanium is more than twice as heavy as silicon.

Germanium, found in nature, is a mixture of five stable isotopes with mass numbers 76, 74, 73, 32, 70. Back in 1871, the famous chemist, "father" of the periodic table, Dmitry Ivanovich Mendeleev predicted the properties and existence of germanium. He called the element unknown at that time "ekasilicium", because. the properties of the new substance were in many respects similar to those of silicon. In 1886, after studying the mineral argyrdite, the German forty-eight-year-old chemist K. Winkler discovered a completely new chemical element in the natural mixture.

At first, the chemist wanted to call the element neptunium, because the planet Neptune was also predicted much earlier than it was discovered, but then he learned that such a name had already been used in the false discovery of one of the elements, so Winkler decided to abandon this name. The scientist was offered to name the element angularium, which means “controversial, angular”, but Winkler did not agree with this name either, although element No. 32 really caused a lot of controversy. The scientist was German by nationality, so he eventually decided to name the element germanium, in honor of his native country of Germany.

As it turned out later, germanium turned out to be nothing more than the previously discovered “ekasilicium”. Up until the second half of the twentieth century, the practical usefulness of germanium was rather narrow and limited. The industrial production of metal began only as a result of the beginning of the industrial production of semiconductor electronics.

Germanium is a semiconductor material widely used in electronics and engineering, as well as in the production of microcircuits and transistors. Radar installations use thin films of germanium, which are applied to glass and used as resistance. Alloys with germanium and metals are used in detectors and sensors.

The element does not have such strength as tungsten or titanium, it does not serve as an inexhaustible source of energy like plutonium or uranium, the electrical conductivity of the material is also far from the highest, and iron is the main metal in industrial technology. Despite this, germanium is one of the most important components of the technical progress of our society, because. it even earlier than silicon began to be used as a semiconductor material.

In this regard, it would be appropriate to ask: What is semiconductivity and semiconductors? Even experts cannot answer this question exactly, because. we can talk about the specifically considered property of semiconductors. There is also an exact definition, but only from the field of folklore: A semiconductor is a conductor for two cars.

A bar of germanium costs almost the same as a bar of gold. The metal is very fragile, almost like glass, so if you drop such an ingot, there is a high probability that the metal will simply break.

Germanium metal, properties

Biological properties

For medical needs, germanium was most widely used in Japan. The results of tests of organogermanium compounds on animals and humans have shown that they are able to have a beneficial effect on the body. In 1967, the Japanese doctor K. Asai discovered that organic germanium has a wide biological effect.

Among all its biological properties, it should be noted:

  • - ensuring the transfer of oxygen to the tissues of the body;
  • - increasing the immune status of the body;
  • - manifestation of antitumor activity.

Subsequently, Japanese scientists created the world's first medical product containing germanium - "Germanium - 132".

In Russia, the first domestic drug containing organic germanium appeared only in 2000.

The processes of biochemical evolution of the surface of the earth's crust did not have the best effect on the content of germanium in it. Most of the element has been washed from the land into the oceans, so that its content in the soil remains quite low.

Among plants that have the ability to absorb germanium from the soil, the leader is ginseng (germanium up to 0.2%). Germanium is also found in garlic, camphor and aloe, which are traditionally used in the treatment of various human diseases. In vegetation, germanium is found in the form of carboxyethyl semioxide. Now it is possible to synthesize sesquioxanes with a pyrimidine fragment - organic compounds of germanium. This compound in its structure is close to natural, as in the root of ginseng.

Germanium can be attributed to rare trace elements. It is present in a large number of different products, but in meager doses. The daily intake of organic germanium is set at 8-10 mg. An assessment of 125 foodstuffs showed that about 1.5 mg of germanium enters the body daily with food. The content of the trace element in 1 g of raw foods is about 0.1 - 1.0 μg. Germanium is found in milk, tomato juice, salmon, and beans. But in order to satisfy the daily need for germanium, you should drink 10 liters of tomato juice daily or eat about 5 kilograms of salmon. From the point of view of the cost of these products, the physiological properties of a person, and common sense, the use of such a quantity of germanium-containing products is also not possible. On the territory of Russia, about 80-90% of the population has a lack of germanium, which is why special preparations have been developed.

Practical studies have shown that in the body germanium is most of all in the current intestine, stomach, spleen, bone marrow and blood. The high content of the microelement in the intestines and stomach indicates a prolonged action of the process of absorption of the drug into the blood. There is an assumption that organic germanium behaves in the blood in much the same way as hemoglobin, i.e. has a negative charge and is involved in the transfer of oxygen to the tissues. Thus, it prevents the development of hypoxia at the tissue level.

As a result of repeated experiments, the property of germanium to activate T-killers and promote the induction of gamma interferons, which suppress the process of reproduction of rapidly dividing cells, was proved. The main direction of action of interferons is antitumor and antiviral protection, radioprotective and immunomodulatory functions of the lymphatic system.

Germanium in the form of sesquioxide has the ability to act on hydrogen ions H +, smoothing out their detrimental effect on body cells. The guarantee of excellent operation of all systems of the human body is the uninterrupted supply of oxygen to the blood and all tissues. Organic germanium not only delivers oxygen to all points of the body, but also promotes its interaction with hydrogen ions.

  • - Germanium is a metal, but its brittleness can be compared to glass.
  • - Some reference books state that germanium has a silvery color. But this cannot be said, because the color of germanium directly depends on the method of processing the surface of the metal. Sometimes it can appear almost black, other times it has a steely color, and sometimes it can be silvery.
  • - Germanium was found on the surface of the sun, as well as in the composition of meteorites that fell from space.
  • - For the first time, an organoelement compound of germanium was obtained by the discoverer of the element Clemens Winkler from germanium tetrachloride in 1887, it was tetraethylgermanium. Of all the organoelement compounds of germanium obtained at the present stage, none is poisonous. At the same time, most of the tin and organolead microelements, which are analogues of germanium in their physical properties, are toxic.
  • - Dmitri Ivanovich Mendeleev predicted three chemical elements even before their discovery, including germanium, calling the element ekasilicium due to its similarity to silicon. The prediction of the famous Russian scientist was so accurate that it simply amazed scientists, incl. and Winkler, who discovered germanium. The atomic weight according to Mendeleev was 72, in reality it was 72.6; the specific gravity according to Mendeleev was 5.5 in reality - 5.469; atomic volume according to Mendeleev was 13 in reality - 13.57; the highest oxide according to Mendeleev is EsO2, in reality - GeO2, its specific gravity according to Mendeleev was 4.7, in reality - 4.703; chloride compound according to Mendeleev EsCl4 - liquid, boiling point about 90 ° C, in fact - chloride compound GeCl4 - liquid, boiling point 83 ° C, compound with hydrogen according to Mendeleev EsH4 is gaseous, compound with hydrogen is actually GeH4 gaseous; organometallic compound according to Mendeleev Es(C2H5)4, boiling point 160 °C, organometallic compound in reality - Ge(C2H5)4 boiling point 163.5°C. As can be seen from the information reviewed above, Mendeleev's prediction was surprisingly accurate.
  • - On February 26, 1886, Clemens Winkler began his letter to Mendeleev with the words "Dear Sir." He, in a rather polite manner, told the Russian scientist about the discovery of a new element, called germanium, which, in its properties, was nothing other than the previously predicted Mendeleev's "ekasilicium." Dmitri Ivanovich Mendeleev's answer was no less polite. The scientist agreed with the discovery of his colleague, calling germanium "the crown of his periodic system", and Winkler the "father" of the element worthy of wearing this "crown".
  • - Germanium as a classical semiconductor has become the key to solving the problem of creating superconducting materials that operate at the temperature of liquid hydrogen, but not liquid helium. As you know, hydrogen passes into a liquid state from a gaseous state when the temperature reaches –252.6°C, or 20.5°K. In the 1970s, a film of germanium and niobium was developed, the thickness of which was only a few thousand atoms. This film is capable of maintaining superconductivity even at temperatures of 23.2°K and below.
  • - When growing a germanium single crystal, a germanium crystal is placed on the surface of molten germanium - a “seed”, which is gradually raised by an automatic device, while the melt temperature slightly exceeds the melting point of germanium (937 ° C). The "seed" rotates so that the single crystal, as they say, "overgrown with meat" from all sides evenly. It should be noted that during such growth, the same thing happens as in the process of zone melting, i.e. practically only germanium passes into the solid phase, and all impurities remain in the melt.

Story

The existence of such an element as germanium was predicted back in 1871 by Dmitry Ivanovich Mendeleev, due to its similarities with silicon, the element was called ekasilicium. In 1886, a professor at the Freiberg Mining Academy discovered argyrodite, a new silver mineral. Then this mineral was studied quite carefully by the professor of technical chemistry Clemens Winkler, conducting a complete analysis of the mineral. Forty-eight-year-old Winkler was rightfully considered the best analyst at the Freiberg Mining Academy, which is why he was given the opportunity to study argyrodite.

In a fairly short time, the professor was able to provide a report on the percentage of various elements in the original mineral: silver in its composition was 74.72%; sulfur - 17.13%; ferrous oxide - 0.66%; mercury - 0.31%; zinc oxide - 0.22%. But almost seven percent - it was the share of some incomprehensible element, which, it seems, had not yet been discovered at that distant time. In connection with this, Winkler decided to isolate the unidentified component of argyrodptus, to study its properties, and in the process of research he realized that he had actually found a completely new element - it was an explication predicted by D.I. Mendeleev.

However, it would be wrong to think that Winkler's work went smoothly. Dmitry Ivanovich Mendeleev, in addition to the eighth chapter of his book Fundamentals of Chemistry, writes: “At first (February 1886), the lack of material, as well as the absence of a spectrum in the flame and the solubility of germanium compounds, seriously hampered Winkler’s research ...” It is worth paying attention to the words “ no spectrum. But how so? In 1886 there was already a widely used method of spectral analysis. Using this method, elements such as thallium, rubidium, indium, cesium on Earth and helium on the Sun were discovered. Scientists already knew for certain that each chemical element without exception has an individual spectrum, and then suddenly there is no spectrum!

The explanation for this phenomenon appeared a little later. Germanium has characteristic spectral lines. Their wavelength is 2651.18; 3039.06 Ǻ and a few more. However, they all lie within the ultraviolet invisible part of the spectrum, it can be considered lucky that Winkler is an adherent of traditional methods of analysis, because it is these methods that led him to success.

Winkler's method of obtaining germanium from the mineral is quite close to one of the modern industrial methods for isolating the 32nd element. First, germanium, which was contained in argaroid, was converted into dioxide. Then the resulting white powder was heated to a temperature of 600-700 °C in a hydrogen atmosphere. In this case, the reaction turned out to be obvious: GeO 2 + 2H 2 → Ge + 2H 2 O.

It was by this method that the relatively pure element No. 32, germanium, was first obtained. At first, Winkler intended to name vanadium neptunium, after the planet of the same name, because Neptune, like germanium, was first predicted, and only then found. But then it turned out that such a name had already been used once, one chemical element, discovered falsely, was called neptunium. Winkler chose not to compromise his name and discovery, and abandoned neptunium. One French scientist Rayon suggested, however, later he recognized his proposal as a joke, he suggested calling the element angular, i.e. "controversial, angular", but Winkler did not like this name either. As a result, the scientist independently chose a name for his element, and named it germanium, in honor of his native country of Germany, over time, this name was established.

Until the 2nd floor. 20th century practical use of germanium remained rather limited. The industrial production of metal arose only in connection with the development of semiconductors and semiconductor electronics.

Being in nature

Germanium can be classified as a trace element. In nature, the element does not occur in its free form at all. The total metal content in the earth's crust of our planet by mass is 7 × 10 −4% %. This is more than the content of such chemical elements as silver, antimony or bismuth. But germanium's own minerals are quite scarce and very rare in nature. Almost all of these minerals are sulfosalts, for example, germanite Cu 2 (Cu, Fe, Ge, Zn) 2 (S, As) 4, confieldite Ag 8 (Sn,Ce)S 6, argyrodite Ag8GeS6 and others.

The main part of germanium dispersed in the earth's crust is contained in a huge number of rocks, as well as many minerals: sulfite ores of non-ferrous metals, iron ores, some oxide minerals (chromite, magnetite, rutile and others), granites, diabases and basalts. In the composition of some sphalerites, the content of the element can reach several kilograms per ton, for example, in frankeite and sulvanite 1 kg / t, in enargites the content of germanium is 5 kg / t, in pyrargyrite - up to 10 kg / t, but in other silicates and sulfides - tens and hundreds g/t. A small proportion of germanium is present in almost all silicates, as well as in some of the oil and coal deposits.

The main mineral of the element is germanium sulfite (formula GeS2). The mineral is found as an impurity in zinc sulfites and other metals. The most important germanium minerals are: germanite Cu 3 (Ge, Fe, Ga) (S, As) 4, plumbogermanite (Pb, Ge, Ga) 2 SO 4 (OH) 2 2H 2 O, stottite FeGe (OH) 6, rhenierite Cu 3 (Fe, Ge, Zn) (S, As) 4 and argyrodite Ag 8 GeS 6 .

Germanium is present in the territories of all states without exception. But none of the industrialized countries of the world has industrial deposits of this metal. Germanium is very, very dispersed. On Earth, minerals of this metal are considered to be very rare, the content of germanium in which is at least 1%. Such minerals include germanite, argyrodite, ultramafic, and others, including minerals discovered in recent decades: schtotite, renierite, plumbogermanite, and confieldite. The deposits of all these minerals are not able to meet the needs of modern industry in this rare and important chemical element.

The bulk of germanium is dispersed in minerals of other chemical elements, and is also found in natural waters, in coals, in living organisms and in soil. For example, the content of germanium in ordinary coal sometimes reaches more than 0.1%. But such a figure is quite rare, usually the share of germanium is lower. But there is almost no germanium in anthracite.

Receipt

During the processing of germanium sulfide, oxide GeO 2 is obtained, with the help of hydrogen it is reduced to obtain free germanium.

In industrial production, germanium is mined mainly as a by-product from the processing of non-ferrous metal ores (zinc blende, zinc-copper-lead polymetallic concentrates containing 0.001-0.1% germanium), ash from coal combustion, and some coke products.

Initially, germanium concentrate (from 2% to 10% germanium) is isolated from the sources discussed above in various ways, the choice of which depends on the composition of the raw material. In the processing of boxing coals, germanium is partially precipitated (from 5% to 10%) into the tar water and resin, from there it is extracted in combination with tannin, after which it is dried and fired at a temperature of 400-500 ° C. The result is a concentrate that contains about 30-40% germanium, germanium is isolated from it in the form of GeCl 4 . The process of extracting germanium from such a concentrate, as a rule, includes the same stages:

1) The concentrate is chlorinated with hydrochloric acid, a mixture of acid and chlorine in an aqueous medium, or other chlorinating agents, which can result in technical GeCl 4 . In order to purify GeCl 4, rectification and extraction of impurities of concentrated hydrochloric acid are used.

2) Hydrolysis of GeCl 4 is carried out, the hydrolysis products are calcined until GeO 2 oxide is obtained.

3) GeO is reduced with hydrogen or ammonia to pure metal.

Upon receipt of the purest germanium, which is used in semiconductor technical means, the zone melting of the metal is carried out. Single-crystal germanium, necessary for semiconductor production, is usually obtained by zone melting or by the Czochralski method.

Methods for isolating germanium from tar waters of coke plants were developed by the Soviet scientist V.A. Nazarenko. In this raw material, germanium is not more than 0.0003%, however, using an oak extract from them, it is easy to precipitate germanium in the form of a tannide complex.

The main component of tannin is an ester of glucose, where the meta-digallic acid radical is present, which binds germanium, even if the concentration of the element in solution is very low. From the sediment, you can easily get a concentrate, the content of germanium dioxide in which is up to 45%.

Subsequent transformations will already depend little on the type of raw material. Germanium is reduced with hydrogen (as in the case of Winkler in the 19th century), however, germanium oxide must first be isolated from numerous impurities. The successful combination of the qualities of one germanium compound proved to be very useful for solving this problem.

Germanium tetrachloride GeCl4. is a volatile liquid that boils at just 83.1°C. Therefore, it is quite conveniently purified by distillation and rectification (in quartz columns with packing).

GeCl4 is almost insoluble in hydrochloric acid. This means that the dissolution of HCl impurities can be used to purify it.

Purified germanium tetrachloride is treated with water, purified with ion-exchange resins. A sign of the desired purity is an increase in the resistivity of water to 15-20 million ohm cm.

Hydrolysis of GeCl4 occurs under the action of water:

GeCl4 + 2H2O → GeO2 + 4HCl.

It can be seen that we have before us the "written backwards" equation for the reaction of obtaining germanium tetrachloride.

Then comes the reduction of GeO2 using purified hydrogen:

GeO2 + 2 H2O → Ge + 2 H2O.

As a result, powdered germanium is obtained, which is alloyed and then purified by the zone melting method. This purification method was developed back in 1952 specifically for the purification of germanium.

The impurities necessary to give germanium a particular type of conductivity are introduced at the final stages of production, namely during zone melting, as well as during the growth of a single crystal.

Application

Germanium is a semiconductor material used in electronics and technology in the production of microcircuits and transistors. The thinnest films of germanium are applied to glass and used as resistance in radar installations. Alloys of germanium with various metals are used in the manufacture of detectors and sensors. Germanium dioxide is widely used in the production of glasses that have the property of transmitting infrared radiation.

Germanium telluride has been serving as a stable thermoelectric material for a very long time, as well as a component of thermoelectric alloys (thermo-mean emf with 50 μV/K). Ultra-high purity germanium plays an exceptionally strategic role in the manufacture of prisms and lenses for infrared optics. The largest consumer of germanium is precisely infrared optics, which is used in computer technology, missile sighting and guidance systems, night vision devices, mapping and the study of the earth's surface from satellites. Germanium is also widely used in fiber optic systems (adding germanium tetrafluoride to glass fibers), as well as in semiconductor diodes.

Germanium as a classical semiconductor has become the key to solving the problem of creating superconducting materials that operate at the temperature of liquid hydrogen, but not liquid helium. As you know, hydrogen passes into a liquid state from a gaseous state when the temperature reaches -252.6°C, or 20.5°K. In the 1970s, a film of germanium and niobium was developed, the thickness of which was only a few thousand atoms. This film is capable of maintaining superconductivity even at temperatures of 23.2°K and below.

By fusing indium into the HES plate, thus creating a region with the so-called hole conductivity, a rectifying device is obtained, i.e. diode. The diode has the property to pass electric current in one direction: the electron region from the region with hole conduction. After indium is fused on both sides of the HES plate, this plate becomes the basis of the transistor. For the first time in the world, a germanium transistor was created back in 1948, and after only twenty years, hundreds of millions of such devices were produced.

Diodes based on germanium and triodes have become widely used in televisions and radios, in a wide variety of measuring equipment and calculating devices.

Germanium is also used in other especially important areas of modern technology: in measuring low temperatures, in detecting infrared radiation, etc.

The use of the broom in all these areas requires germanium of very high chemical and physical purity. Chemical purity is such a purity at which the amount of harmful impurities should not be more than one ten-millionth of a percent (10-7%). Physical purity means a minimum of dislocations, a minimum of disturbances in the crystal structure of a substance. To achieve it, single-crystal germanium is specially grown. In this case, the entire metal ingot is just one crystal.

To do this, a germanium crystal is placed on the surface of molten germanium - a "seed", which gradually rises using an automatic device, while the melt temperature slightly exceeds the melting point of germanium (937 ° C). The "seed" rotates so that the single crystal, as they say, "overgrown with meat" from all sides evenly. It should be noted that during such growth, the same thing happens as in the process of zone melting, i.e. practically only germanium passes into the solid phase, and all impurities remain in the melt.

Physical properties

Probably, few of the readers of this article had to visually see vanadium. The element itself is quite scarce and expensive, they do not make consumer goods from it, and their germanium filling, which happens in electrical appliances, is so small that it is not possible to see the metal.

Some reference books state that germanium is silver in color. But this cannot be said, because the color of germanium directly depends on the method of processing the surface of the metal. Sometimes it can appear almost black, other times it has a steely color, and sometimes it can be silvery.

Germanium is such a rare metal that the cost of its ingot can be compared with the cost of gold. Germanium is characterized by increased brittleness, which can only be compared with glass. Outwardly, germanium is quite close to silicon. These two elements are both competitors for the title of the most important semiconductor and analogues. Although some of the technical properties of the element are largely similar, as regards the appearance of the materials, it is very easy to distinguish germanium from silicon, germanium is more than twice as heavy. The density of silicon is 2.33 g/cm3 and the density of germanium is 5.33 g/cm3.

But it is impossible to speak unambiguously about the density of germanium, because. the figure 5.33 g/cm3 refers to germanium-1. This is one of the most important and most common modification of the five allotropic modifications of the 32nd element. Four of them are crystalline and one is amorphous. Germanium-1 is the lightest of the four crystalline modifications. Its crystals are built exactly the same as diamond crystals, a = 0.533 nm. However, if this structure is maximally dense for carbon, then germanium also has denser modifications. Moderate heat and high pressure (about 30 thousand atmospheres at 100 ° C) converts germanium-1 into germanium-2, the crystal lattice structure of which is exactly the same as that of white tin. We use the same method to obtain germanium-3 and germanium-4, which are even denser. All these "not quite ordinary" modifications are superior to germanium-1 not only in density, but also in electrical conductivity.

The density of liquid germanium is 5.557 g/cm3 (at 1000°C), the melting temperature of the metal is 937.5°C; the boiling point is about 2700°C; the value of the thermal conductivity coefficient is approximately 60 W / (m (K), or 0.14 cal / (cm (sec (deg)) at a temperature of 25 ° C. At ordinary temperatures, even pure germanium is fragile, but when it reaches 550 ° C, it begins to succumb On the mineralogical scale, the hardness of germanium is from 6 to 6.5, the value of the compressibility coefficient (in the pressure range from 0 to 120 H / m 2, or from 0 to 12000 kgf / mm 2) is 1.4 10-7 m 2 /mn (or 1.4 10-6 cm 2 /kgf), the surface tension is 0.6 n/m (or 600 dynes/cm).

Germanium is a typical semiconductor with a band gap size of 1.104·10 -19 or 0.69 eV (at 25°C); in high purity germanium, the electrical resistivity is 0.60 ohm (m (60 ohm (cm) (25 ° C); the electron mobility index is 3900, and the hole mobility is 1900 cm 2 / in. sec (at 25 ° C and at content from 8% of impurities.) For infrared rays, the wavelength of which is more than 2 microns, the metal is transparent.

Germanium is rather brittle, it cannot be hot or cold worked by pressure below 550 °C, but if the temperature rises, the metal becomes ductile. The hardness of the metal on the mineralogical scale is 6.0-6.5 (germanium is sawn into plates using a metal or diamond disk and an abrasive).

Chemical properties

Germanium, being in chemical compounds, usually exhibits the second and fourth valencies, but compounds of tetravalent germanium are more stable. Germanium at room temperature is resistant to the action of water, air, as well as alkali solutions and dilute concentrates of sulfuric or hydrochloric acid, but the element dissolves quite easily in aqua regia or an alkaline solution of hydrogen peroxide. The element is slowly oxidized by the action of nitric acid. Upon reaching a temperature of 500-700 ° C in air, germanium begins to oxidize to GeO 2 and GeO oxides. (IV) germanium oxide is a white powder with a melting point of 1116°C and a solubility in water of 4.3 g/l (at 20°C). According to its chemical properties, the substance is amphoteric, soluble in alkali, with difficulty in mineral acid. It is obtained by penetration of the hydrated precipitate GeO 3 nH 2 O, which is released during hydrolysis Germanium acid derivatives, for example, metal germanates (Na 2 GeO 3 , Li 2 GeO 3 , etc.) are solids with high melting points, can be obtained by fusing GeO 2 and other oxides.

As a result of the interaction of germanium and halogens, the corresponding tetrahalides can be formed. The reaction is easiest to proceed with chlorine and fluorine (even at room temperature), then with iodine (temperature 700-800 ° C, presence of CO) and bromine (with low heating). One of the most important germanium compounds is tetrachloride (formula GeCl 4). It is a colorless liquid with a melting point of 49.5°C, a boiling point of 83.1°C and a density of 1.84 g/cm3 (at 20°C). The substance is strongly hydrolyzed by water, releasing a precipitate of hydrated oxide (IV). The tetrachloride is obtained by chlorination of metallic germanium or by the interaction of GeO 2 oxide and concentrated hydrochloric acid. Germanium dihalides with the general formula GeX 2 , hexachlorodigermane Ge 2 Cl 6 , GeCl monochloride, as well as germanium oxychlorides (for example, CeOCl 2) are also known.

Upon reaching 900-1000 ° C, sulfur interacts vigorously with germanium, forming GeS 2 disulfide. It is a white solid with a melting point of 825°C. The formation of GeS monosulfide and similar compounds of germanium with tellurium and selenium, which are semiconductors, are also possible. At a temperature of 1000–1100 °C, hydrogen slightly reacts with germanium, forming germine (GeH) X, which is an unstable and highly volatile compound. Germanic hydrogens of the series Ge n H 2n + 2 to Ge 9 H 20 can be formed by reacting germanides with dilute HCl. Germylene is also known with the composition GeH 2 . Germanium does not react directly with nitrogen, but there is Ge 3 N 4 nitride, which is obtained by the action of ammonia on germanium (700-800 ° C). Germanium does not interact with carbon. With many metals, germanium forms various compounds - germanides.

Many complex compounds of germanium are known, which are becoming increasingly important in the analytical chemistry of the element germanium, as well as in the processes of obtaining a chemical element. Germanium is able to form complex compounds with hydroxyl-containing organic molecules (polyhydric alcohols, polybasic acids, and others). There are also germanium heteropoly acids. Like other Group IV elements, germanium characteristically forms organometallic compounds. An example is tetraethylgermane (C 2 H 5) 4 Ge 3 .

The chemical element germanium is in the fourth group (main subgroup) in the periodic table of elements. It belongs to the family of metals, its relative atomic mass is 73. By mass, the content of germanium in the earth's crust is estimated at 0.00007 percent by mass.

Discovery history

The chemical element germanium was established thanks to the predictions of Dmitry Ivanovich Mendeleev. It was he who predicted the existence of ecasilicon, and recommendations were given for its search.

He believed that this metal element is found in titanium, zirconium ores. Mendeleev tried on his own to find this chemical element, but his attempts were unsuccessful. Only fifteen years later, at a mine located in Himmelfurst, a mineral was found, called argyrodite. This compound owes its name to the silver found in this mineral.

The chemical element germanium in the composition was discovered only after a group of chemists from the Freiberg Mining Academy began research. Under the guidance of K. Winkler, they found out that only 93 percent of the mineral is accounted for by oxides of zinc, iron, as well as sulfur, mercury. Winkler suggested that the remaining seven percent came from a chemical element unknown at the time. After additional chemical experiments, germanium was discovered. The chemist announced his discovery in a report, presented the information received on the properties of the new element to the German Chemical Society.

The chemical element germanium was introduced by Winkler as a non-metal, by analogy with antimony and arsenic. The chemist wanted to call it neptunium, but that name had already been used. Then it began to be called germanium. The chemical element discovered by Winkler caused a serious discussion among the leading chemists of the time. The German scientist Richter suggested that this is the same exasilicon that Mendeleev spoke of. Some time later, this assumption was confirmed, which proved the viability of the periodic law created by the great Russian chemist.

Physical properties

How can germanium be characterized? The chemical element has 32 serial number in Mendeleev. This metal melts at 937.4 °C. The boiling point of this substance is 2700 °C.

Germanium is an element that was first used in Japan for medical purposes. After numerous studies of organogermanium compounds conducted on animals, as well as in the course of studies on humans, it was possible to find a positive effect of such ores on living organisms. In 1967, Dr. K. Asai succeeded in discovering the fact that organic germanium has a huge spectrum of biological effects.

Biological activity

What is the characteristic of the chemical element germanium? It is able to carry oxygen to all tissues of a living organism. Once in the blood, it behaves by analogy with hemoglobin. Germanium guarantees the full functioning of all systems of the human body.

It is this metal that stimulates the reproduction of immune cells. It, in the form of organic compounds, allows the formation of gamma-interferons, which inhibit the reproduction of microbes.

Germanium prevents the formation of malignant tumors, prevents the development of metastases. Organic compounds of this chemical element contribute to the production of interferon, a protective protein molecule that is produced by the body as a protective reaction to the appearance of foreign bodies.

Areas of use

The antifungal, antibacterial, antiviral property of germanium has become the basis for its areas of application. In Germany, this element was mainly obtained as a by-product of the processing of non-ferrous ores. Germanium concentrate was isolated by various methods, which depend on the composition of the feedstock. It contained no more than 10 percent of the metal.

How exactly is germanium used in modern semiconductor technology? The characteristic of the element given earlier confirms the possibility of its use for the production of triodes, diodes, power rectifiers, and crystal detectors. Germanium is also used in the creation of dosimetric instruments, devices that are necessary to measure the strength of a constant and alternating magnetic field.

An essential area of ​​application of this metal is the manufacture of infrared radiation detectors.

It is promising to use not only germanium itself, but also some of its compounds.

Chemical properties

Germanium at room temperature is quite resistant to moisture and atmospheric oxygen.

In the series - germanium - tin), an increase in the reducing ability is observed.

Germanium is resistant to solutions of hydrochloric and sulfuric acids, it does not interact with alkali solutions. At the same time, this metal dissolves rather quickly in aqua regia (seven nitric and hydrochloric acids), as well as in an alkaline solution of hydrogen peroxide.

How to give a complete description of a chemical element? Germanium and its alloys must be analyzed not only in terms of physical and chemical properties, but also in terms of applications. The process of oxidation of germanium with nitric acid proceeds rather slowly.

Being in nature

Let's try to characterize the chemical element. Germanium is found in nature only in the form of compounds. Among the most common germanium-containing minerals in nature, we single out germanite and argyrodite. In addition, germanium is present in zinc sulfides and silicates, and in small amounts in various types of coal.

Harm to health

What effect does germanium have on the body? A chemical element whose electronic formula is 1e; 8 e; 18 e; 7 e, can adversely affect the human body. For example, when loading a germanium concentrate, grinding, as well as loading the dioxide of this metal, occupational diseases may appear. As other sources that are harmful to health, we can consider the process of remelting germanium powder into bars, obtaining carbon monoxide.

Adsorbed germanium can be quickly excreted from the body, mostly with urine. Currently, there is no detailed information on how toxic germanium inorganic compounds are.

Germanium tetrachloride has an irritating effect on the skin. In clinical trials, as well as with long-term oral administration of cumulative amounts that reached 16 grams of spirogermanium (an organic antitumor drug), as well as other germanium compounds, nephrotoxic and neurotoxic activity of this metal was found.

Such dosages are generally not typical for industrial enterprises. Those experiments that were carried out on animals were aimed at studying the effect of germanium and its compounds on a living organism. As a result, it was possible to establish a deterioration in health when inhaling a significant amount of dust of metallic germanium, as well as its dioxide.

Scientists have found serious morphological changes in the lungs of animals, which are similar to proliferative processes. For example, a significant thickening of the alveolar sections was revealed, as well as hyperplasia of the lymphatic vessels around the bronchi, thickening of the blood vessels.

Germanium dioxide does not irritate the skin, but direct contact of this compound with the membrane of the eye leads to the formation of germanic acid, which is a serious ocular irritant. With prolonged intraperitoneal injections, serious changes in peripheral blood were found.

Important Facts

The most harmful germanium compounds are germanium chloride and germanium hydride. The latter substance provokes serious poisoning. As a result of a morphological examination of the organs of animals that died during the acute phase, they showed significant disturbances in the circulatory system, as well as cellular modifications in the parenchymal organs. Scientists came to the conclusion that hydride is a multi-purpose poison that affects the nervous system and depresses the peripheral circulatory system.

germanium tetrachloride

It is a strong irritant to the respiratory system, eyes, and skin. At a concentration of 13 mg/m 3 it is able to suppress the pulmonary response at the cellular level. With an increase in the concentration of this substance, there is a serious irritation of the upper respiratory tract, significant changes in the rhythm and frequency of breathing.

Poisoning with this substance leads to catarrhal-desquamative bronchitis, interstitial pneumonia.

Receipt

Since in nature germanium is present as an impurity to nickel, polymetallic, tungsten ores, several labor-intensive processes associated with ore enrichment are carried out in industry to isolate pure metal. First, germanium oxide is isolated from it, then it is reduced with hydrogen at an elevated temperature to obtain a simple metal:

GeO2 + 2H2 = Ge + 2H2O.

Electronic properties and isotopes

Germanium is considered an indirect-gap typical semiconductor. The value of its permittivity is 16, and the value of electron affinity is 4 eV.

In a thin film doped with gallium, it is possible to give germanium a state of superconductivity.

There are five isotopes of this metal in nature. Of these, four are stable, and the fifth undergoes double beta decay, with a half-life of 1.58×10 21 years.

Conclusion

Currently, organic compounds of this metal are used in various industries. Transparency in the infrared spectral region of metallic ultra-high purity germanium is important for the manufacture of optical elements of infrared optics: prisms, lenses, optical windows of modern sensors. The most common use of germanium is the creation of optics for thermal imaging cameras that operate in the wavelength range from 8 to 14 microns.

Such devices are used in military equipment for infrared guidance systems, night vision, passive thermal imaging, and fire fighting systems. Also, germanium has a high refractive index, which is necessary for anti-reflective coating.

In radio engineering, germanium-based transistors have characteristics that, in many respects, exceed those of silicon elements. The reverse currents of germanium cells are significantly higher than those of their silicon counterparts, which makes it possible to significantly increase the efficiency of such radio devices. Given that germanium is not as common in nature as silicon, silicon semiconductor elements are mainly used in radio devices.

(Germanium; from lat. Germania - Germany), Ge - chemical. element of group IV of the periodic system of elements; at. n. 32, at. m. 72.59. Silvery-gray substance with a metallic sheen. In chem. compounds exhibits oxidation states + 2 and +4. Compounds with an oxidation state of +4 are more stable. Natural germanium consists of four stable isotopes with mass numbers 70 (20.55%), 72 (27.37%), 73(7.67%) and 74 (36.74%) and one radioactive isotope with mass number 76 ( 7.67%) and a half-life of 2,106 years. Artificially (with the help of various nuclear reactions) many radioactive isotopes have been obtained; the most important is the 71 Ge isotope with a half-life of 11.4 days.

The existence of holy germanium (under the name "ekasilitsiy") was predicted in 1871 by the Russian scientist D. I. Mendeleev. However, only in 1886 it. chemist K. Winkler discovered an unknown element in the mineral argyrodite, the properties of which coincided with the properties of "ecasilicon". Beginning of prom. the production of germanium dates back to the 40s. 20th century, when it was used as a semiconductor material. The content of germanium in the earth's crust (1-2) is 10~4%. Germanium is a trace element and is rarely found as its own minerals. Seven minerals are known, in which its concentration is more than 1%, among them: Cu2 (Cu, Ge, Ga, Fe, Zn) 2 (S, As) 4X X (6.2-10.2% Ge), rhenierite (Cu, Fe)2 (Cu, Fe, Ge, Ga, Zn)2 X X (S, As)4 (5.46-7.80% Ge) and argyrodite Ag8GeS6 (3/55-6.93% Ge) . G. also accumulates in caustobioliths (humic coals, oil shale, oil). The crystalline modification of diamond, stable under ordinary conditions, has a cubic structure like diamond, with a period a = 5.65753 A (Gel).

Germanium is

The density of germanium (t-ra 25 ° C) 5.3234 g / cm3, tmelt 937.2 ° C; tbp 2852°C; heat of fusion 104.7 cal/g, heat of sublimation 1251 cal/g, heat capacity (temperature 25°C) 0.077 cal/g deg; coefficient thermal conductivity, (t-ra 0 ° C) 0.145 cal / cm sec deg, temperature coefficient. linear expansion (t-ra 0-260 ° C), 5.8 x 10-6 deg-1. During melting, germanium decreases in volume (by about 5.6%), its density increases by 4% h. At high pressure, a diamond-like modification. Germanium undergoes polymorphic transformations, forming crystalline modifications: a tetragonal structure of the B-Sn type (GeII), a body-centered tetragonal structure with periods a = 5.93 A, c = 6.98 A (GeIII) and a body-centered cubic structure with a period a = 6, 92A(GeIV). These modifications are characterized by higher density and electrical conductivity compared to GeI.

Amorphous germanium can be obtained in the form of films (about 10-3 cm thick) by steam condensation. Its density is less than the density of crystalline G. The structure of energy zones in G. crystal determines its semiconductor properties. The width of the band gap G. is equal to 0.785 eV (t-ra 0 K), the electrical resistivity (t-ra 20 ° C) is 60 ohm cm, and with increasing temperature it decreases significantly according to an exponential law. Impurities give G. t. impurity conductivity of the electronic (impurities of arsenic, antimony, phosphorus) or hole (impurities of gallium, aluminum, indium) type. The mobility of charge carriers in G. (t-ra 25 ° C) for electrons is about 3600 cm2 / v sec, for holes - 1700 cm2 / v sec, the intrinsic concentration of charge carriers (t-ra 20 ° C) is 2.5. 10 13 cm-3. G. is diamagnetic. Upon melting, it transforms into a metallic state. Germanium is very brittle, its Mohs hardness is 6.0, microhardness is 385 kgf/mm2, compressive strength (temperature 20°C) is 690 kgf/cm2. With an increase in t-ry, hardness decreases, above t-ry 650 ° C, it becomes plastic, amenable to fur. processing. Germanium is practically inert to air, oxygen and to non-oxidizing electrolytes (if there is no dissolved oxygen) at temperatures up to 100 ° C. Resistant to the action of hydrochloric and dilute sulfuric acid; slowly dissolves in concentrated sulfuric and nitric acids when heated (the resulting film of dioxide slows down dissolution), dissolves well in aqua regia, in solutions of hypochlorites or alkali hydroxides (in the presence of hydrogen peroxide), in alkali melts, peroxides, nitrates and carbonates of alkali metals.

Above t-ry 600 ° C is oxidized in air and in a stream of oxygen, forming oxide GeO and dioxide (Ge02) with oxygen. Germanium oxide is a dark gray powder sublimating at t-re 710 ° C, slightly soluble in water with the formation of a weak germanite to-you (H2Ge02), a salt swarm (germanites) of low resistance. In to-takh GeO dissolves easily with the formation of salts of divalent H. Germanium dioxide is a white powder, exists in several polymorphic modifications that differ greatly in chemical. St. you: the hexagonal modification of dioxide is relatively well soluble in water (4.53 zU at t-re 25 ° C), alkali solutions and to-t, the tetragonal modification is practically insoluble in water and inert to acids. Dissolving in alkalis, the dioxide and its hydrate form salts of metagermanate (H2Ge03) and orthogermanate (H4Ge04) to-t - germanates. Alkali metal germanates dissolve in water, the remaining germanates are practically insoluble; freshly precipitated dissolve in mineral to-tah. G. easily combines with halogens, forming when heated (about t-ry 250 ° C) the corresponding tetrahalogenides - non-salt-like compounds that are easily hydrolyzed by water. G. are known - dark brown (GeS) and white (GeS2).

Germanium is characterized by compounds with nitrogen - brown nitride (Ge3N4) and black nitride (Ge3N2), characterized by a smaller chemical. tenacity. With phosphorus G. forms a low-resistant phosphide (GeP) of black color. It does not interact with carbon and does not alloy; it forms a continuous series of solid solutions with silicon. Germanium, as an analogue of carbon and silicon, is characterized by the ability to form germanohydrogens of the GenH2n + 2 type (germanes), as well as solid compounds of the GeH and GeH2 types (germenes). Germanium forms metal compounds () and with many others. metals. G.'s extraction from raw materials consists in receiving a rich germanium concentrate, and from it - high purity. In the prom. scale, germanium is obtained from tetrachloride, using its high volatility during purification (for isolation from concentrate), low in concentrated hydrochloric acid and high in organic solvents (for purification from impurities). Often for enrichment use high volatility of the lower sulfide and oxide G., to-rye are easily sublimated.

To obtain semiconductor germanium, directional crystallization and zone recrystallization are used. Monocrystalline germanium is obtained by drawing from the melt. In the process of growing G., special alloys are added. additives, adjusting certain properties of the monocrystal. G. is supplied in the form of ingots with a length of 380-660 mm and a cross section of up to 6.5 cm2. Germanium is used in radio electronics and electrical engineering as a semiconductor material for the manufacture of diodes and transistors. Lenses for infrared optics devices, nuclear radiation dosimeters, X-ray spectroscopy analyzers, sensors using the Hall effect, and converters of radioactive decay energy into electrical energy are made from it. Germanium is used in microwave attenuators, resistance thermometers, operated at a temperature of liquid helium. The G. film deposited on the reflector is distinguished by high reflectivity and good corrosion resistance. germanium with some metals, characterized by increased resistance to acidic aggressive environments, is used in instrument making, mechanical engineering and metallurgy. gemanium with gold form a low-melting eutectic and expand upon cooling. G.'s dioxide is used for the manufacture of special. glass, characterized by a high coefficient. refraction and transparency in the infrared part of the spectrum, glass electrodes and thermistors, as well as enamels and decorative glazes. Germanates are used as activators of phosphors and phosphors.

- a chemical element of the periodic system of chemical elements D.I. Mendeleev. And denoted by the symbol Ge, germanium is a simple substance that is gray-white in color and has solid characteristics like a metal.

The content in the earth's crust is 7.10-4% by weight. refers to trace elements, due to its reactivity to oxidation in the free state, it does not occur as a pure metal.

Finding germanium in nature

Germanium is one of the three chemical elements predicted by D.I. Mendeleev on the basis of their position in the periodic system (1871).

It belongs to rare trace elements.

At present, the main sources of industrial production of germanium are waste from zinc production, coal coking, ash from some certain types of coal, in silicate impurities, sedimentary iron rocks, nickel and tungsten ores, peat, oil, geothermal waters and some algae.

The main minerals containing germanium

Plumbohermatite (PbGeGa) 2 SO 4 (OH) 2 + H 2 O content up to 8.18%

yargyrodite AgGeS6 contains from 3.65 to 6.93% germany.

rhenierite Cu 3 (FeGeZn)(SAs) 4 contains from 5.5 to 7.8% germanium.

In some countries, obtaining germanium is a by-product of the processing of certain ores such as zinc-lead-copper. Germanium is also obtained in the production of coke, as well as in brown coal ash with a content of 0.0005 to 0.3% and in hard coal ash with a content of 0.001 to 1 -2%.

Germanium as a metal is very resistant to the action of atmospheric oxygen, oxygen, water, some acids, dilute sulfuric and hydrochloric acids. But concentrated sulfuric acid reacts very slowly.

Germanium reacts with nitric acid HNO 3 and aqua regia, slowly reacts with caustic alkalis to form a germanate salt, but with the addition of hydrogen peroxide H 2O2 the reaction is very fast.

When exposed to high temperatures above 700 °C, germanium is easily oxidized in air to form GeO 2 , readily reacts with halogens to form tetrahalides.

Does not react with hydrogen, silicon, nitrogen and carbon.

Volatile germanium compounds are known with the following characteristics:

Germany hexahydride-digermane, Ge 2 H 6 - combustible gas, decomposes during long-term storage in the light, turning yellow then brown turning into a dark brown solid, decomposed by water and alkalis.

Germany tetrahydride, monogermane - GeH 4 .

Application of germanium

Germanium, like some others, has the properties of so-called semiconductors. All according to their electrical conductivity are divided into three groups: conductors, semiconductors and insulators (dielectrics). The specific electrical conductivity of metals is in the range 10V4 - 10V6 Ohm.cmV-1, the division given is conditional. However, one can point out a fundamental difference in the electrophysical properties of conductors and semiconductors. For the former, the electrical conductivity decreases with increasing temperature, for semiconductors it increases. At temperatures close to absolute zero, semiconductors turn into insulators. As is known, metallic conductors exhibit the properties of superconductivity under such conditions.

Semiconductors can be various substances. These include: boron, (

And even before silicon, germanium became the most important semiconductor material.

Here the question is appropriate: what are semiconductors and semiconductors? Even experts sometimes find it difficult to answer it unambiguously. "The exact definition of semiconductivity is difficult and depends on what property of semiconductors is considered" - this evasive answer is borrowed from a quite respectable scientific work on semiconductors. True, there is a very clear definition: “A semiconductor is one conductor for two cars,” but this is already from the field of folklore ...

The main thing about element number 32 is that it is a semiconductor. We will return to the explanation of this property later. In the meantime, about germanium as a physicochemical "personality".

germanium as it is

Probably, the vast majority of readers have never seen germanium. This element is quite rare, expensive, consumer goods are not made from it, and the germanium "stuffing" of semiconductor devices is so small that you can see what it is, germanium, difficult, even if the body of the device is broken. Therefore, we will talk about the main properties of germanium, its appearance, features. And you try to mentally do those simple operations that the author had to do more than once.

We extract a standard ingot of germanium from the package. This is a small body of almost regular cylindrical shape, with a diameter of 10 to 35 and a length of several tens of millimeters. Some reference books state that item #32 is silver, but this is not always true: the color of germanium depends on its surface treatment. Sometimes it looks almost black, sometimes it looks like steel, but sometimes it is also silver.

When considering a germanium ingot, do not forget that it costs about the same as gold, and at least for this reason you should not drop it on the floor. But there is another reason, much more important: germanium is almost as brittle as glass and can behave accordingly. I have seen how, after such a failure, a careless experimenter crawled along the floor for a long time, trying to collect all the pieces to a single one ... In appearance, germanium is easy to confuse with silicon. These elements are not only competitors claiming to be the main semiconductor material, but also analogues. However, despite the similarity of many technical properties and appearance, it is quite simple to distinguish a germanium ingot from a silicon ingot: germanium is more than twice as heavy as silicon (density 5.33 and 2.33 g / cm 3, respectively).

The last statement needs to be clarified, although it would seem that the numbers preclude comment. The fact is that the number 5.33 refers to germanium-1 - the most common and most important of the five allotropic modifications of element No. 32. One of them is amorphous, four are crystalline. Of the crystalline germanium-1 is the lightest. Its crystals are built in the same way as diamond crystals, but if such a structure determines the maximum density for carbon, then germanium also has denser “packings”. High pressure with moderate heating (30 thousand atm and 100 ° C) converts Ge-I to Ge-II with a crystal lattice, like white tin.

In a similar way, even denser than Ge-II, Ge-III and Ge-IV can be obtained.

All "unusual" modifications of crystalline germanium are superior to Ge-I and electrical conductivity. The mention of this particular property is not accidental: the value of electrical conductivity (or reciprocal value - resistivity) for a semiconductor element is especially important.

But what is a semiconductor?

Formally, a semiconductor is a substance with a resistivity from thousandths to millions of ohms per 1 cm. The "from" and "to" frames are very wide, but the place of germanium in this range is quite definite. The resistance of a centimeter cube of pure germanium at 18°C ​​is 72 ohms. At 19°C the resistance of the same cube is reduced to 68 ohms. This is generally characteristic of semiconductors - a significant change in electrical resistance with a slight change in temperature. As the temperature rises, the resistance usually decreases. It changes significantly both under the influence of irradiation and during mechanical deformations.

Remarkable is the sensitivity of germanium (as, indeed, of other semiconductors) not only to external influences. The properties of germanium are strongly influenced by even negligible amounts of impurities. The chemical nature of impurities is no less important.

The addition of an element of the V group makes it possible to obtain a semiconductor with an electronic type of conductivity. This is how hydroelectric power stations are prepared (electronic germanium doped with antimony). By adding an element of group III, we will create a hole type of conductivity in it (most often it is GDH - hole germanium doped with gallium).

Recall that “holes” are places vacated by electrons that have passed to another energy level. The "apartment" vacated by the migrant can be immediately occupied by his neighbor, but he also had his own apartment. Resettlements are made one after another, and the hole moves.

The combination of areas with electronic and hole conduction formed the basis of the most important semiconductor devices - diodes and transistors. For example, by fusing indium into a HES plate and thus creating a region with hole conduction, we obtain a rectifying device - a diode. It passes electric current mainly in one direction - from the area with hole conductivity to the electronic one. Having melted indium on both sides of the HPP plate, we turn this plate into the basis of the transistor.

The world's first germanium transistor was created in 1948, and after 20 years hundreds of millions of such devices were produced. Germanium diodes and triodes are widely used in radios and televisions, computers and various measuring equipment.

Germanium is also used in other paramount areas of modern technology: for measuring low temperatures, for detecting infrared radiation, etc. All these areas require germanium of very high purity - physical and chemical. The chemical purity is such that the amount of harmful impurities does not exceed one ten-millionth of a percent (107%). Physical purity is a minimum of dislocations, disturbances in the crystal structure. To achieve it, single-crystal germanium is grown: the entire ingot is one crystal.

For this incredible purity

In the earth's crust, germanium is not very small - 7 * 10 -4% of its mass. This is more than lead, silver, tungsten. Germanium is found on the Sun and in meteorites. Germany is present in all countries. But industrial deposits of germanium minerals, apparently, do not have any industrialized country. Germanium is very scattered. Minerals in which this element is more than 1% - argyrodite, germanite, ultramafic and others, including renierite, shtotite, confieldite and plumbogermanite discovered only in recent decades - are very rare. They are unable to cover the world's need for this important element.

And the bulk of terrestrial germanium is dispersed in minerals of other elements, in coals, in natural waters, in soil and living organisms. In coal, for example, the content of germanium can reach a tenth of a percent. Maybe, but it doesn't always reach. In anthracite, for example, it is almost absent ... In a word, germanium is everywhere and nowhere.

Therefore, the methods of concentration of germanium are very complex and varied. They depend primarily on the type of raw material and the content of this element in it.

Academician Nikolai Petrovich Sazhin was the head of the comprehensive study and solution of the germanium problem in the USSR. How the Soviet semiconductor industry was born is described in his article published in the journal "Chemistry and Life" a year and a half before the death of this outstanding scientist and organizer of science.

Pure germanium dioxide was obtained for the first time in our country at the beginning of 1941. It was used to make germanium glass with a very high refractive index of light. Research on element No. 32 and methods for its possible production resumed after the war, in 1947. Now scientists were interested in germanium precisely as a semiconductor.

New methods of analysis helped to reveal a new source of germanium raw materials - tar waters of coke plants. Germany in them is not more than 0.0003%, but with the help of an oak extract from them it turned out to be easy to precipitate germanium in the form of a tannide complex. The main component of tannin is a glucose ester. It is able to bind germanium even if the concentration of this element in solution is vanishingly small.

From the resulting precipitate, destroying the organic matter, it is easy to obtain a concentrate containing up to 45% germanium dioxide.

Further transformations depend little on the type of raw material. Germanium is reduced with hydrogen (as Winkler did), but first you need to separate germanium oxide from numerous impurities. To solve this problem, a successful combination of the properties of one of the germanium compounds turned out to be very useful.

Germanium tetrachloride GeCl 4 is a volatile liquid with a low boiling point (83.1°C). Therefore, it is convenient to purify it by distillation and rectification (the process takes place in quartz columns with a packing). Germanium tetrachloride is almost insoluble in concentrated hydrochloric acid. Therefore, the dissolution of impurities with hydrochloric acid can be used to purify GeCl 4 .

Purified GeCl4 is treated with water, from which almost all contaminants were previously removed using ion-exchange resins. A sign of the desired purity is an increase in the resistivity of water to 15-20 million ohm-cm.

Under the action of water, germanium tetrachloride is hydrolyzed: GeCl 4 + 2H 2 O → GeO 2 + 4HCl. Note that this is the “reversed” equation of the reaction in which germanium tetrachloride is obtained. This is followed by the reduction of GeO 2 with purified hydrogen: GeO 2 + 2H 2 → Ge + 2H 2 O. Powdered germanium is obtained, which is alloyed and then further purified by zone melting. By the way, this method of purification of materials was developed in 1952 specifically for the purification of semiconductor germanium.

Impurities necessary to give germanium one or another type of conductivity (electronic or hole) are introduced at the last stages of production, i.e., during zone melting and in the process of growing a single crystal.

Ever since it was found in 1942 that it would be advantageous to replace part of the vacuum tubes in radar systems with semiconductor detectors, interest in germanium has grown from year to year. The study of this previously unused element contributed to the development of science in general and, above all, of solid state physics. And the importance of semiconductor devices - diodes, transistors, thermistors, strain gauges, photodiodes and others - for the development of radio electronics and technology in general is so great and so well known that it is worth talking about. in lofty tones once again somehow uncomfortable. Until 1965, most semiconductor devices were made on a germanium basis. But in subsequent years, the process of gradual displacement of “ecasilicon” by silicium itself began to develop.

Germanium under the pressure of silicon

Silicon semiconductor devices compare favorably with germanium devices primarily by better performance at elevated temperatures and lower reverse currents. The great advantage of silicon was also the resistance of its dioxide to external influences. It was she who made it possible to create a more progressive - planar technology for the production of semiconductor devices, consisting in the fact that a silicon plate is heated in oxygen or a mixture of oxygen with water vapor and it is covered with a protective layer of SiO 2.

Having then etched the "windows" in the right places, dopants are introduced through them, contacts are connected here, and the device as a whole, meanwhile, is protected from external influences. For germanium, such a technology is not yet possible: the stability of its dioxide is insufficient. Under the onslaught of silicon, gallium arsenide and other semiconductors, germanium lost its position as the main semiconductor material. In 1968, the United States was producing far more silicon transistors than germanium ones. Now the world production of germanium, according to foreign experts, is 90-100 tons per year. His position in technology is quite strong.

  • First, semiconductor germanium is noticeably cheaper than semiconductor silicon.
  • Secondly, it is easier and more profitable to make some semiconductor devices, as before, from germanium, and not from silicon.
  • Thirdly, the physical properties of germanium make it practically indispensable in the manufacture of certain types of devices, in particular, tunnel diodes.

All this gives reason to believe that the value of germanium will always be great.

ANOTHER ACCURATE PREDICTION. Much has been written about the foresight of D. I. Mendeleev, who described the properties of three yet undiscovered elements. Not wanting to repeat ourselves, we just want to draw attention to the accuracy of the Mendeleev forecast. Compare the data of Mendeleev and Winkler summarized in the table.

Ekasilicon Atomic weight 72 Specific gravity 5.5 Atomic volume 13 Higher oxide EsO 2 Its specific gravity 4.7

Chloride compound EsCl 4 - liquid with a boiling point of about 90 ° C

Hydrogen bond EsH 4 gaseous

Organometallic compound Es(C2H 5) 4 with a boiling point of 160°C

Germanium Atomic weight 72.6 Specific gravity 5.469 Atomic volume 13.57 Higher oxide GeO 2 Its specific gravity 4.703

Chloride compound GeCl 4 - liquid with a boiling point of 83 ° C

Hydrogen bond GeH 4 gaseous

Organometallic compound Ge (C2H 5) 4 with a boiling point of 163.5 ° C

LETTER FROM CLEMENS WINKLER

"Your Majesty!

Permit me herewith to give you a reprint of the message, from which it follows that I have discovered a new element "germanium". At first I was of the opinion that this element filled the gap between antimony and bismuth in your wonderfully penetratingly constructed periodic system and that this element coincides with your ekaantimony, but everything indicates that we are dealing here with ekasilicium.

I hope to tell you soon more about this interesting substance; today I confine myself to notifying you of the very probable triumph of your brilliant research and testifying to you my respect and deep respect.

MENDELEEV ANSWERED: “Since the discovery of germanium is the crown of the periodic system, then you, as the “father” of germanium, own this crown; for me, my role as a predecessor and the friendly attitude that I met with you is valuable.

GERMANIUM AND ORGANICS. The first organoelement compound of element No. 32, tetraethylgermanium, was obtained by Winkler from germanium tetrachloride. Interestingly, none of the germanium organoelement compounds obtained so far is toxic, while most lead and organotin compounds (these elements are analogs of germanium) are toxic.

HOW GERMANIUM MONOCRYSTAL IS GROWN. A germanium crystal is placed on the surface of molten germanium - a “seed”, which is gradually raised by an automatic device; the melt temperature is slightly higher than the melting point of germanium (937°C). The seed is rotated so that the single crystal "overgrown with meat" evenly from all sides. It is important that in the process of such growth, the same thing happens as in zone melting: almost exclusively germanium passes into the “build-up” (solid phase), and most of the impurities remain in the melt.

GERMANIUM AND SUPERCONDUCTIVITY. The classical semiconductor germanium turned out to be involved in solving another important problem - the creation of superconducting materials operating at the temperature of liquid hydrogen, and not liquid helium. Hydrogen, as is known, passes from a gaseous to a liquid state at a temperature of -252.6 ° C, or 20.5 ° K. In the early 70s, a film was obtained from an alloy of germanium with niobium with a thickness of only a few thousand atoms. This film retains superconductivity at temperatures of 24.3°K and below.