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 conductivity formed the basis of the most important semiconductor devices - diodes and transistors. For example, 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 diverse. 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 influence 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 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.
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.
DEFINITION
Germanium is the thirty-second element of the Periodic Table. Designation - Ge from the Latin "germanium". Located in the fourth period, IVA group. Refers to semimetals. The nuclear charge is 32.
In the compact state, germanium has a silvery color (Fig. 1) and looks like a metal in appearance. At room temperature, it is resistant to air, oxygen, water, hydrochloric acid and dilute sulfuric acid.
Rice. 1. Germanium. Appearance.
Atomic and molecular weight of germanium
DEFINITION
Relative molecular weight of a substance (M r) is a number showing how many times the mass of a given molecule is greater than 1/12 of the mass of a carbon atom, and relative atomic mass of an element (A r)- how many times the average mass of atoms of a chemical element is greater than 1/12 of the mass of a carbon atom.
Since germanium exists in the free state in the form of monatomic Ge molecules, the values of its atomic and molecular masses coincide. They are equal to 72.630.
Isotopes of germanium
It is known that germanium can occur in nature in the form of five stable isotopes 70 Ge (20.55%), 72 Ge (20.55%), 73 Ge (7.67%), 74 Ge (36.74%) and 76 Ge (7.67%). Their mass numbers are 70, 72, 73, 74 and 76, respectively. The nucleus of the germanium isotope 70 Ge contains thirty-two protons and thirty-eight neutrons, the remaining isotopes differ from it only in the number of neutrons.
There are artificial unstable radioactive isotopes of germanium with mass numbers from 58 to 86, among which the 68 Ge isotope with a half-life of 270.95 days is the longest-lived.
germanium ions
On the outer energy level of the germanium atom, there are four electrons that are valence:
1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 2 .
As a result of chemical interaction, germanium gives up its valence electrons, i.e. is their donor, and turns into a positively charged ion:
Ge 0 -2e → Ge 2+;
Ge 0 -4e → Ge 4+.
Molecule and atom of germanium
In the free state, germanium exists in the form of monatomic Ge molecules. Here are some properties that characterize the germanium atom and molecule:
Examples of problem solving
EXAMPLE 1
EXAMPLE 2
| Exercise | Calculate the mass fractions of the elements that make up germanium (IV) oxide if its molecular formula is GeO 2 . |
| Solution | The mass fraction of an element in the composition of any molecule is determined by the formula: ω (X) = n × Ar (X) / Mr (HX) × 100%. |
(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-tah, GeO dissolves easily with the formation of salts of divalent G. Germanium dioxide is a white powder, exists in several polymorphic modifications that differ greatly in chemical composition. 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. On a scale, germanium is obtained from tetrachloride, using its high volatility during purification (for separation 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, (
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.
