Tellurium is a quasi metallic element, the element symbol Te, in the periodic table family VI A, with an atomic number of 52 and an atomic mass of 127.6. Tellurium comes in two allotropy, a hexagonal system with spirally arranged atoms and a silvery white metallic luster, and an amorphous, black powder. Tellurium has a melting point of 452 °C and a boiling point of 1390 °C. Tellurium is soluble in sulfuric acid, nitric acid, aqua regia, potassium cyanide, potassium hydroxide; insoluble in water, carbon disulfide. Tellurium burns in air with a blue flame, producing tellurium(IV) oxide. The human body inhaled very low concentration of tellurium, in the gas, sweat and urine will produce a pleasant odor of garlic. Tellurium is one of seven rare metals that are associated with minerals. Isolated deposits are rare, as is tellurium.

1. 1782 Müller, a mine supervisor in Vienna, Austria, was the first to extract tellurium when he discovered a mineral known locally as "strange gold" in a mine in Romania, he took it back to the lab and extracted a small amount of the silver-gray substance, which he initially thought was antimony, but later found to be different and determined to be a new metallic element, although there was no definitive proof, he could only seek confirmation from other chemists, so he sent a few samples to Bergman, a Swedish chemist, for identification. However, due to the small number of samples, Borgman was only able to prove that it was not antimony. Müller's findings had to be shelved. It wasn't until 16 years later, when the German mineralogist Klaproth read a paper on Transylvania's gold deposits at the Prussian Academy of Sciences on Jan. 25, that the long forgotten element was reintroduced. Klaproth, who extracted tellurium from gold, dissolved the ore in Aqua Regia, partially precipitated the solution with an excess of Alkali, removing gold and iron, and discovered the new element in the precipitate, which he named tellurium, with the element symbol Te. The word comes from the Latin, tellus. Klaproth has repeatedly stated that the new element was discovered by 1782 Müller.

2. The discovery of Spain's supergiant tellurium deposit 2016 has been an extraordinary year for tellurium resources, a giant super tellurium rich deposit has been found in an undersea mountain range southwest of Canary Islands, Spain (see Reference News, April 17,2017) , by an international team led by British scientists, multiple signs of tellurium abundance have been found. Bram Murton, who led the team that discovered the deposit, estimates tellurium reserves could reach 26,70T, or one twelfth of the world's known reserves, if the calculations are confirmed, the undersea mine will be the world's largest super tellurium mine, because it is a tellurium-rich ore that is extremely beneficial for the extraction of pure tellurium. The Undersea Mountain Range was formed about 119 million years ago and its highest peak is about 1,100 meters above sea level. The research team was led by scientists from the UK's National Centre for Marine Research, researchers and professors from the Spanish Institute of Geology and Mining, the British Geological Survey, the University of Southampton and the University of S?o Paulo took part. The tellurium mine is covered by a hard layer of rock about 40 mm in the outer layer of the seamounts, said the head of the research and exploration team, who analyzed and studied rock and ore samples collected by an underwater robot, it is the richest tellurium deposit ever found in the world, and its tellurium grade is much higher than that of any deposit on land. Prior to the expedition, the Spanish Institute of Geology and Mining and the Spanish Institute of Oceanography had also conducted several geological surveys and surveys of the seamounts and had claimed that they might contain minerals of industrial exploitation value, and this joint exploration with British scientists to achieve multi-faceted results is undoubtedly a milestone of great significance.

3. Tellurium is a Non-ferrous metal, a semi metal, with two allotropic variants: Crystalline and Amorphous. Crystalline tellurium has a silvery white metallic appearance, isomorphous With Gray Selenium B, and Amorphous tellurium is black powder. Tellurium has an extremely low electrical conductivity base, 1.6105 cm at 0 °C, and increases slightly in the presence of trace impurities. It has a melting point of 449.8 °C and a boiling point of 988 °C, also known as 1390 °C in Literature. The density of crystallized tellurium is 6.25 g/cm3 at 20 °C, the density of Amorphous tellurium is 6.015 g/cm3, the average specific heat of 0 ° ー100 °C is 134 j/(kg k) , the melting heat is 17.6 Kj/mol, the vaporization heat of TE2 is 107.6 Kj/mol, and the average thermal conductivity of 0 ° ー100 °C is 3.8 w/(M K) . It has a mohs hardness of 2.5, a Trouton constant of 13.2, and tellurium is insoluble in all solvents that do not react with it. The molecular weight of tellurium in the greenhouse has not been determined. The chemical formula of tellurium is TE2 at 1400 °C ~ 1800 °C, and the Te-Te distance is 2.6 a. The Red Sol of tellurium in water is prepared by reduction of tellurium acid with hydrazine. Tellurium burns in the air, producing a blue flame that forms tellurium(IV) oxide. Tellurium can react with halogen, but not with sulfur and selenium. Tellurium, in contrast to Selenium, rarely reacts with hydrogen at High Temperatures. Tellurium is soluble in solutions of sulfuric acid, nitric acid, potassium hydroxide, and potassium cyanide. Te (IV) , such as TEO2 or Tete (VI) valence state, such as Pb32H2(TEO6) , can be reduced to simple substance under the conditions of reduction and acid medium.

4. Tellurium, the world's tellurium resource, as well as China's, has a mass fraction of 110 to 6 percent in the Earth's crust, which is rare and less than its companion element, selenium, but added to the 2670 terabytes of seabed rich deposits discovered last year in the Canary Islands, Spain, that will raise its reserves to a higher value. Tellurium is a sulfur-friendly element, so it is mostly enriched in the crust in the form of sulfides. Common Copper Sulfide Ores and polymetallic ores are copper sulfide ores. The tellurium content in pyrite and mercury antimony ores is the highest. The tellurium content in gold ores is also higher. The tellurium content in coal mines is about 0.015 g/t, tELLURIUM RESERVES: 50 KT in 2016. Small amounts of tellurium can also be recovered from gold telluride ores. tellurium in undeveloped, ungraded or undiscovered copper and other metal resources contains several times as much as tellurium in identified industrial copper ores; The reserves of coal are about four times that of copper. Unfortunately, existing technologies are not yet effective in extracting tellurium from gold and coal mines. China now has the third largest amount of associated tellurium reserves in the world, second only to the United States and Canada. China has discovered 24 associated tellurium mines, with about 12 KT reserves, which are distributed in 16 provinces and regions of the country, mainly concentrated in Guangdong, accounting for 43% , 42% ; Gansu, 10% . Tellurium deposits in China are mainly associated with copper, lead, zinc and other metallic minerals. Based on the calculation of the main mineral reserves, there are about 10 kt tellurium resources in China that are not included in the reserves. Tellurium resources in China are concentrated in hydrothermal polymetallic deposits, sicarite-type copper deposits and magmatic cu-ni sulfide deposits, accounting for 44.77% , 43.89% and 11.34% of associated tellurium reserves respectively. DABAOSHAN copper mine in Qujiang, Chengmenshan copper mine in Jiangxi Province and Baijiazuizi mine in Jinchuan, Gansu Province are the three largest associated tellurium deposits in China, which account for 94% of the total reserves in China. There are two stories to tell here. First, in August 1991, the world's first case of independent tellurium was discovered in Dashuigou, Shimian County, Sichuan Province, China, thus, the traditional idea that the dispersed element tellurium "can form independent minerals, but there is no exploitable independent deposit" has been completely changed, which fills a gap in the theory of deposit science and rewrites the understanding of the ore-forming ability of the dispersed element, at the same time, it will change the existing pattern that can only extract associated tellurium from other minerals, and change the distribution pattern of tellurium resources. The second is the discovery of a new mineral, tungsten tellurite, by Chinese scientists in 2014, by Professor Li Guowu of the China University of Geosciences's single crystal x-ray diffraction crystal Structure Laboratory, in October 2014, it was approved and approved by the mineral classification and new Mineral Nomenclature Committee of the International Mineralogical Society. The new mineral, found in half of the weathered granite in Huaping County, Yunnan Province, is a new mineral with a new composition and structure composed of tellurium and tungsten and potassium, which is the first time in the world to be found, k-TE-W is the only natural mineral of K-Te-W. No similar natural mineral has been found before. The new mineral is named "Tungsten tellurite" because of its special composition. Its crystal structure has the derivative structure of w-bronze type structure. Weak satellite diffraction points were observed by single crystal diffraction, and two-dimensional non-co-modulation structure was found, which may be caused by the shift of occupancy or Valence and vacancy of K and Te and W. The discovery of tellurium, which forms tungsten-telluride oxides with tungsten and potassium, is the first of its kind, it is of great theoretical and practical significance to study the crystal chemistry of tellurium, the newly independent tellurium deposit and the new type of granite tellurium deposit.

5. Except for a small amount of tellurium found in central Europe, Bolivia and China, tellurium minerals are mostly associated with pyrite, chalcopyrite and Sphalerite, and the yield is only 0.001% ~ 0.1% . Tellurium minerals such as AUTE2, Bi2Tes2 and tellurite are rare and of no mining value, almost all of them are recovered from the anode of refining copper and lead, and the anode slime of copper electrorefining is the main raw material for extracting tellurium, the basic process of treating anode slime is sulfuric acid roasting, and other processes such as Soda sintering are seldom used. According to the content of tellurium in anode slime, different processes can be adopted. The anode slime with high tellurium content (about 3%) was first roasted by sulfuric acid at 250 °C, and then volatilized at about 700 °C. The tellurium was left in the selenium dioxide, and the copper sulfate in the slag was first leached by water, then leached by NaOH solution, and then dissolved by sodium tellurite, after purification, the precipitates were dissolved in NaOH solution, and the concentration of tellurium in the solution was kept at 100g/l. The purity of 98% ~ 99% tellurium can be prepared by electrolysis at 160g/l Naoh. The mixture of copper anode slime and lead anode with low tellurium content can be reduced to 98% industrial tellurium after reduction smelting and a series of treatment. High Purity tellurium was prepared by electrolysis, with industrial tellurium as anode, polyvinyl chloride membrane as outer surface, stainless steel plate as cathode, sodium tellurite Na2TeO3 solution as electrolyte, TEO2 concentration 168g/l ~ 183g/l, electrolytic temperature 45 °C, current density 200A/m 2, 4N5 tellurium can be obtained on the cathode. High Purity tellurium of 5N can be obtained from Te by distillation in vacuum furnace at 460 °C ~ 500 °C and 0.0133 ~ 0.133 n/m2. Based on the principle that H2 can react with Se but not with Te, the impurity Se can be further removed and 6N tellurium can be obtained.

6. TELLURIUM: A cutting-edge material that supports the development of high-precision technologies. The application fields of tellurium are traditional and high-precision technologies. In the former field, it is mainly used as trace alloying element and chemical catalyst, in the latter area is in the photoelectric and thermoelectric. Effective trace alloying elements of steel and Non-ferrous metal alloys: addition of 0.04% te to low carbon high speed cutting steel and high strength steel can improve their machinability, and the cutting speed can be increased to 195mmin, three times higher than normal; Adding 0.01% te ~ 0.1% te to malleable cast iron can remarkably refine grain, and 14500 free-cutting copper containing 0.5% te has good machinability, high electrical conductivity, thermal conductivity and fatigue resistance, etc. , adding 0.01% Te ~ 0.5% Te to aluminum, tin and lead alloys can improve their corrosion resistance and hardness. Lead alloys containing Te are good materials for submarine cables. Tellurium accounted for about 45 per cent of total consumption in metallurgy in 2015 and about 500t worldwide. The application of tellurium in high technology refers to photoelectric and thermoelectricity: The nuclear radiation detectors made by CdTe have large forbidden broadband, wavelength coordination range up to 0.4 m ~ 50 M, and are allowed to work at room temperature. PBTE, Hgcdte, PBSNTE and so on are good materials for making night vision mirror, infrared detector, laser and infrared radar. BI2(TE1-XSEX)3, (B1-XSbX) TE3 and PBTE are excellent materials for semiconductor refrigeration, which can be used as molecular sieve for radar, underwater missile cooling, submarine air conditioning and CO2 removal, electronic Component, flight suits and civilian electronic refrigerators, medicine chests and liquor cabinets, as well as cooling caps for pilots and special personnel, have been used effectively in thermal power generation, for example, the Gesi/pbte series generator is a very reliable power source, which has become a good power source for spaceflight, missile launching, missile buoy and telemetry recorder, although its thermal-electrical conversion is only 10% , much lower than that of 14% of SI and 22% of GAAS, its absorption of solar and infrared wavelengths is 33∶1, much higher than that of other known materials, and has the advantages of low cost and portability, it has been widely used in spacecraft, especially in satellite. Tellurium is not consumed in the field of photoelectricity, but the components it synthesizes have excellent performance, so it has very high added value. Due to the rapid development of the semiconductor refrigeration industry in China, the consumption of tellurium has risen sharply, and it has the potential to catch up with the later, by 2020 it is likely to overtake metallurgy, and thermoelectric and photovoltaic fields are likely to become the biggest consumers of tellurium. Tellurium powder is used as the second vulcanizing agent to prevent the aging of low-sulfur or non-sulfur rubber and the decrease of mechanical properties The oxides of tellurium can be used as reaction catalysts for the oxidation, hydrogenation and dehydrogenation of organic chemical processes, and the salts of tellurium can be used as antioxidants for the removal of oil sludge in lubricating oil, as well as solid lubricants and detonators for timing detonation. Tellurium applications in the chemical industry have been fairly stable at about 22% .

7.The application fields of tellurium in its early stage are rather limited. During World War II, tellurium was used in natural rubber production as a vulcanizing agent and did not become an element of industrial use until the late 1950s. Tellurium and its compounds are widely used. The downstream industries include solar energy, alloy, thermoelectric refrigeration, electronics, rubber and so on. Cadmium telluride (CDTE) thin film solar energy industry is developing rapidly and is considered as one of the most promising solar energy technologies. With the development of cdte thin film Solar Energy Industry, the demand for telluride will continue to grow rapidly.

01. Main products of tellurium the main products of tellurium include: tellurium metal, tellurium(IV) oxide, tellurium powder and high purity tellurium. 

02. Application domain distribution of tellurium\

03. Tellurium accounts for 42% of the total amount of application in metallurgical industry. Due to the rapid development of tellurium in photovoltaic field, the proportion of metallurgical industry tends to decrease. Tellurium is mainly used in metallurgy as an alloying element in Non-ferrous metal and steel. In the Non-ferrous metal industry, tellurium is used to improve the machinability of copper alloys, to increase the hardness and plasticity of tin, aluminum, and lead based alloys, and to make cable sheaths such as oil submersible pumps. Adding 0.03%-0.04% tellurium into cast iron and steel can reduce nitrogen absorption of cast iron and steel, change the grain size of steel, improve the strength and corrosion resistance of steel. Adding 0.001%-0.002% tellurium into cast iron can make its surface firm and wear resistant, tellurium has an important effect on the microstructure, crystallization process and mechanical properties of cast iron, and its tendency to white is the first of all elements. The tellurium-treated steel has been used in mines, automation, railways and other equipment. 04. The chemical industry chemical industry accounts for about 21% of total tellurium applications. In the field of chemical industry, tellurium and tellurium compounds are used as additives of catalysts and dispersants in the rubber industry to improve the strength and elasticity of rubber. Tellurium plays an important role in nickel electrolysis. Adding Nateo3(75 ml/l) to the electrolyte results in an over-layer of nickel, which eventually forms a corrosion-resistant nickel layer. Tellurium catalysts have been used in petroleum cracking and coal hydrogenation. Tellurium can also prevent the oxidation of Polymethylsiloxane. Tellurium has also been used as a toner and solid lubricant in photography and printing. In addition, Bismuth telluride is an ideal substitute for CFC-11 and CFC-12 in human refrigeration industry (refrigerators, air conditioners, etc.) due to its excellent refrigeration properties. 05. Tellurium accounts for about 8% of the consumption in the electrical and electronic industry. In the optoelectronics industry, lasers, photodiodes and photoreceivers which involve infrared to ultraviolet spectra all use semiconductor components such as Znte, CdTe, HgTe, HgCdTe, etc. . Lead, tin, Mercury and cadmium tellurides are sensitive to infrared radiation. PBSNTE and CdHgTe compounds are important infrared photoelectric materials, and tellurium is an important raw material for producing infrared materials. Due to the high photosensitivity of Sete and SeAs alloys per unit time, Hgcdte is the main photosensitive material for infrared detectors in military and aerospace systems, and CdTe is used in photoelectric systems because of its good absorption properties, the US military uses 99.99999% pure tellurium. Based on the excellent photosensitivity of tellurium compounds, it has shown outstanding advantages in resources survey, satellite aerial survey, laser guidance and so on. Tellurium is an important photoresistive element in photographic plate-making, laser printing and photocopying. Tellurium's ability to do this in photonics is what makes it one of the most attractive industries of the 21st century.

06. Cadmium telluride thin film Solar Cell 1) What is cadmium telluride thin film solar cell? CdTe thin film solar cells, or CdTe cells for short, are thin film solar cells based on P CdTe and n type CD heterojunction. General Standard CdTe thin film solar cells are composed of five layers: back electrode, back contact layer, CdTe absorption layer, CdTe window layer, TCO layer. At present, CdTe cells can be prepared by many methods, such as near-space sublimation, chemical bath deposition (CBD) , screen printing, sputtering, evaporation and so on. In general, the methods of CBD are used in industrialization and laboratory because of the low cost of CBD method and the Good Compact connection between CdS and TCO. 2) global overview of cadmium telluride thin-film Solar cells global manufacturers of cadmium telluride thin-film Solar cells are Canada's 5NPlus, Redlen and leading thin-film materials, of which 5NPlus is the world's First large-scale producer of cadmium telluride for thin-film Solar power. It is currently the world's largest producer of cadmium telluride for thin-film Solar power, with a large market share in the sector, which has grown rapidly with the growth of First Solar, its main customer, with about 75 per cent of its sales coming from First Solar. Redlen is one of the world's leading producers of radiation detectors and medical imaging equipment, and one of the few companies in the world with technology to produce cadmium telluride for thin-film solar power. It has a small market share in cadmium telluride products due to the lack of an integrated industrial chain. CDTE for thin film solar energy has been developed since 2006. It has passed the quality certification of some customers and has the technical capability of mass production. 3) the development status and trend of domestic CDTE thin film Solar Cell Industry in 1980s, the research work of CDTE thin film solar cell in China began formally. Initially, the Inner Mongolia University used evaporation and electrodeposition techniques (ED) to study and prepare CdTe thin film cells, which achieved an efficiency of 5.8% . From the mid-1980s to the mid-1990s, the research work was basically at a standstill with very few results. In the late 1990s, Professor Feng Lianghuan of the Sichuan University led the research on cadmium telluride thin film solar cells. During the ninth five-year Plan period, he undertook the research project of "the development of ii-vi Compound semiconductor polycrystalline thin film solar cells" funded by the Ministry of Science and technology. Near-space sublimation technique has been used to study CdTe thin film batteries, and good results have been obtained. Recently, the efficiency of the battery has broken through 13.38% , which is among the most advanced in the world. During the tenth five-year Plan period, CdTe thin film battery research was included in the 863 Program 863 key projects. Through the unremitting efforts of several generations of scientists, our country is in the rapid development stage from basic laboratory research to application industrialization, and plans to set up a pilot production line with an annual output of 0.5 mw. CDTE thin film solar cell research, from the original only Inner Mongolia University, Sichuan University, Xinjiang University and other institutions in this area of basic research, to this year's Sichuan Apollo Solar Technology Development Co. , Ltd..NewwCDTEE thin filmCDTEE CdSSOLARRCELLLCOREeMATERIALSsINDUSTRIALIZATIONn, over a period of two years, will build a 50 tons of cadmium telluride production line, cadmium sulfide 10 tons production line,Chinaa will be in thin film solar cell industrialization will be developed, to the world leading level. 4) problems and constraints cadmium telluride thin film solar cell fabrication process is relatively easy, so compared with other solar thin film solar cells its commercialization progress is the fastest. From laboratory research stage to large-scale industrial production. At present, the next research and development focus of CdTe solar cells is how to further reduce costs, improve efficiency and improve and perfect production process. At present, the market share of CdTe batteries is not ideal. The reasons why CdTe cells can not become the mainstream of the market are as follows: 01. Modules and substrates cost too much, with List of semiconductor materials accounting for 53% of the total cost, of which only about 5.5% . 02. Due to the limited natural transport capacity of tellurium, the total amount of tellurium can not meet the need of large and overall reliance on this kind of photovoltaic power generation. 03 Cadmium's toxicity, causes the people not to be able to accept this kind of photocell confidently. CdTe solar cells as large-scale production and application of photovoltaic devices, environmental pollution is not negligible. Toxic element cadmium (CD) pollution of the environment as well as the health of operators is not negligible. We can not access clean energy while at the same time causing new harm to the human body and the human living environment. It is not technically difficult to efficiently process CdTe modules that are abandoned or broken. But cadmium is a highly toxic heavy metal, and its compounds are also toxic. The main effects of cadmium are: First, the harm of Cd-containing dust to human and other animals through inhalation; second, the ecological pollution caused by the discharge of waste water from production. Therefore, the CD and Te on the broken glass should be removed and recovered, the damaged and discarded components should be treated properly, and the waste water and waste from the production should be treated in accordance with environmental standards. At present, all countries are working to solve the factors that restrict the development of CdTe thin film solar cells. I believe these problems will be solved one by one, so that CdTe thin film solar cells will become one of the new energy components in the future society.

8. Other tellurium can also be used as a colorant for glass and ceramics. tellurium-containing materials can be added to produce glass and ceramics in different colors Tellurium is added to make the glaze pink. Compared with ordinary silicate glass, tellurium glass has the characteristics of high refractive index, low deformation temperature, high density and infrared transparency. Glasses containing a certain amount of Germanium, sulfur and tellurium have good chemical properties in the infrared region, high mechanical strength, good heat resistance (softening point 385 °c) and heat shock resistance. The transparent property of tellurium glass is helpful to the application of infrared optics, such as being used as infrared window. The good photosensitivity indicates that it can be used as a photoconductive camera tube with low softening temperature, and it is possible to make semiconductor materials for vacuum sealing. Tellurium compounds have obvious anti-tumor effect and inhibit the proliferation of leukemic cells. In addition, it can be used in insecticides, fungicides, the production of radionuclide, can also be used to treat hair loss, syphilis and other diseases. It is found that tellurium and its compounds are less toxic than selenium, water soluble tellurite and tellurite are the most toxic, and element tellurium is the least toxic. For tellurium, the United Nations, the United States and a number of countries and organizations have proposed exposure thresholds for health standards. 

Source: Web Collation

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