What Is Tellurium – The Define Of Tellurium Alloy
Tellurium is a quasi metal element with the element symbol Te. It belongs to Group VI A in the periodic table of elements. Its atomic number is 52 and its atomic mass is 127.6. Tellurium has two allotropes, one belongs to hexagonal crystal system, with spiral atomic arrangement and silver white metallic luster; The other is amorphous, black powder. Tellurium has a melting point of 452 ℃ and a boiling point of 1390 ℃. It is brittle and similar in chemical properties to antimony. Tellurium is soluble in sulfuric acid, nitric acid, aqua regia, potassium cyanide and potassium hydroxide; It is insoluble in water and carbon disulfide. Tellurium burns in air with a blue flame to form tellurium dioxide.
After the human body inhales tellurium of extremely low concentration, it will produce an unpleasant garlic odor in the breath, sweat and urine. Tellurium is one of the seven rare and dispersed metals, which are generally associated minerals. Independent deposits are rare, as is tellurium. Dashuigou tellurium bismuth pyrite deposit in Shimian County, Sichuan Province, China is the only tellurium primary deposit in the world so far. In view of the scarcity of resource reserves and relatively small tellurium production, the United States, Canada, Peru, China and Russia supply relatively large quantities of tellurium. Because of the huge market demand for cadmium telluride thin film solar cells, cadmium telluride is currently the most demanding and promising telluride products. Tellurium is used in metallurgy, electronics and chemistry.
A Brief History Of The Discovery Of Tellurium And Its Industrial Development
In 1782, Franz Joseph Muller, a mine supervisor in Vienna, the capital of Austria, was the first person to extract tellurium. He found an ore called “strange gold” in a mine in Romania. He took it back to the laboratory and extracted a small amount of silver gray material from it. At first, he thought it was antimony, but later found that the two were different in nature, so it was determined to be a new metal element. However, there was no exact evidence, He could only seek confirmation from other chemists, so he sent a few samples to the Swedish chemist Bergman for identification. However, due to the small number of samples, Bergman can only prove that it is not antimony. Mueller’s discovery had to be shelved.
It was not until 16 years later that M.H. Klaproth, a German mineralogist, read a paper on gold deposits in Transylvania at the Academy of Sciences in Berlin on January 25, 1798 that he put forward this long forgotten element again. Claptote extracted tellurium from gold mine. He dissolved the ore in aqua regia, precipitated part of the solution with excessive alkali to remove gold and iron, found this new element in the precipitation, named it tellurium (tellurium), and determined the element symbol as Te. The word comes from the Latin tellus (Earth). Claptott has repeatedly stated that this new element was discovered by Mueller in 1782.
Development of Tellurium Industry
Tellurium consumption is expected to decline, mainly due to the decline in solar cell production in the field where tellurium consumption is the largest. With the development of science and technology, solar cells and thermal electronic products are also upgrading, and manufacturers tend to save costs through recycling and other ways. Due to the high price of tellurium, the demand for tellurium in the Alloy field and the chemical industry will also decline. Many low-end tellurium product manufacturers are increasingly inclined to look for raw materials to replace tellurium. However, in the long run, it is expected that the price of tellurium will continue to rise, and the profits of tellurium products, especially high-purity tellurium and cadmium telluride products with high technical threshold, will remain at a high level. Driven by the explosive growth of the thin-film solar industry, downstream enterprises have an increasing demand for tellurium before finding suitable substitutes.
The use of tellurium is constantly improving. As a country rich in tellurium resources, China must attach importance to the development and utilization of tellurium resources, strengthen the protection of tellurium resources and the management and supervision of their development and utilization, and rely on scientific and technological progress to improve the protection and rational utilization of tellurium resources. Experience our team in the market competition of global resource development, and enhance China’s scientific, technological and economic strength in the development, production and utilization of tellurium resources.
Tellurium Resource Reserves And Mineral Output
Existence in nature
The crustal abundance of tellurium is lx10-7%, and no independent industrial mineral of tellurium has been found. Tellurium ore resources are distributed sparsely, and most of them are associated with other minerals or exist in other minerals in the form of impurities. Dashuigou tellurium bismuth pyrite deposit in Shimian County, Sichuan Province, China is the only “tellurium independent primary deposit” reported so far in the world, and is known as the “second national treasure” after giant pandas. Tellurium is mainly associated with pyrite, chalcopyrite and sphalerite, with the content of 0.001% – 0.1%; The main tellurium minerals are galena, tellurite, bismuth tellurite, tellurite, gold telluride, copper telluride, etc. The above minerals are rare and have no industrial value. At present, it is mainly extracted and prepared from anode slime of electrolytic copper, smoke and dust of zinc smelting, gold, silver, lead and other refining tailings.
According to the data released by the United States Geological Survey (USGS) in 2015, the global tellurium resource reserves reached 24000 tons, and the United States, Peru, Canada, Japan and Russia are relatively rich in tellurium resources. However, USGS statistics are based on copper resources, because before the 1990s, it was generally believed that most of the world’s recoverable tellurium was associated with copper deposits. However, in recent years, the discovery and geological exploration of a series of important telluride type gold and silver deposits at home and abroad have shown that the geochemical properties of dispersed element tellurium are much more active than those traditionally recognized, and it can be enriched and mineralized on a large scale to form independent ore deposits or industrial ore bodies with economic value. Such as Sichuan Shimian Dashuigou tellurium bismuth gold deposit, Shandong Guilaizhuang tellurium gold deposit, Henan Beiling telluride type gold deposit, etc. This makes people have to have a new understanding of the distribution of tellurium resources.
According to the exploration data in China, the proven associated tellurium reserves in China now rank the third in the world. Associated tellurium mineral resources are relatively rich. About 30 associated tellurium mineral sites have been found nationwide, with reserves of nearly 14000 tons. Tellurium mining areas are distributed in 16 provinces (districts) in China. However, the reserves are mainly concentrated in Guangdong, Jiangxi, Gansu and other provinces. Tellurium ores in China are also mainly associated with copper, lead zinc and other metal minerals. According to the calculation of the main mineral reserves, there are about 10000 tons of tellurium ore resources not included in the reserves in China. This will change the distribution pattern of tellurium resources and may make China a large country of tellurium resources. According to the data of the Ministry of Land and Resources, the statistical table of mineral resources reserves in Hubei Province (as of the end of 2011) shows that there are 2 tellurium mining areas, 116 tons of resource reserves have been identified, and 43.48 tons of retained resource reserves.
Due to the uniqueness of tellurium (one of the rare and dispersed metals) resources, the global annual output is limited, and the number of enterprises in the industry is not large, so it is difficult to calculate specific output data. The latest USGS report in 2015 did not give accurate figures for 2014.
Most enterprises mainly produce fine tellurium or tellurium compounds of 3N or 4N purity, and few enterprises have the technical capacity to produce high-purity tellurium and cadmium telluride of 5N or above purity. Large scale enterprises in the industry include China’s leading thin materials, Jiangxi Copper, 5NPlus in Canada, and PRM in the Philippines. Raw material purchasing capacity, technology research and development capacity, and production capacity determine the comprehensive competitiveness of enterprises. In terms of high-purity tellurium products, global manufacturers include leading thin materials and 5NPlus. In terms of refined tellurium products, the world’s major producers include leading thin materials and PRM, and many other small-scale refined tellurium producers affiliated to copper smelting enterprises.
Tellurium mainly comes from the following ways:
- Recycling from by-products of copper electrolysis is the main source of tellurium at present, accounting for more than 60% of the annual supply of tellurium;
- Recovery of tellurium from by-products of lead refining
- Tellurium is one of the associated metals of gold. With the increase of tellurium price, more and more tellurium is recovered from the by-products formed in the smelting process of near noble metals;
- Tellurium is recovered from the by-products of the production of bismuth telluride thermoelectric refrigeration device and the production of cadmium telluride thin film solar energy. With the large-scale application of cadmium telluride thin film solar cells in the future, it is expected that recovering tellurium from waste cadmium telluride thin film solar cells will become one of the important sources of tellurium;
- To mine tellurium from tellurium ores, the proven tellurium reserves of Dashuigou Tellurium Mine and Majiagou Tellurium Mine in Sichuan Province, China are 328 tons and 437 tons respectively. With the rising price of tellurium, mining tellurium from tellurium ores will become one of the important sources.
According to the latest known accurate data, the global tellurium production in 2010 was about 600 tons, with major tellurium producers in Canada, Japan, China, Peru, the United States, Kazakhstan, Russia and other countries. Jiangxi Copper (50 tons of refined tellurium in 2012), Tongling Nonferrous Metals and other enterprises are large producers of tellurium in China. In the future, with the increase of global copper production and tellurium recovery, the growth rate of tellurium production will be greatly increased. It is estimated that if 80% of tellurium in by-products of copper electrolysis is recovered, the output of tellurium recovered from by-products of copper electrolysis will reach 1295 tons in 2020, which will be much higher than the current output of tellurium.
Extraction Process Of Tellurium
The anode slime obtained from copper electrolytic refining is the main source of tellurium. Generally, this anode slime contains 2% – 10% tellurium, and most of it exists in the form of Ag2Te, Cu2Te, Au2Te, etc. Different copper smelters use different copper raw materials, and the tellurium content of copper anode slime also varies greatly, ranging from 5% to 6% for the high to 0.5% to 0.8% for the low, or even lower, but most of them are about 1%. Due to its special chemical properties, tellurium has obvious amphoteric characteristics, is easy to disperse and has low recovery. Considering the economic benefits, each manufacturer adopts different technological processes. Some factories add tellurium separation process in the process of copper anode slime treatment to recover tellurium. At the same time, in order to reduce the impact of tellurium on product quality (mainly on the quality of silver).
At present, crude tellurium is mainly recovered from by-products of electrolytic copper. The preparation technology of commercial grade fine tellurium is relatively mature, and the technical level at home and abroad is similar. The preparation technology of high-purity tellurium started late in China, and only a few enterprises have mastered the production technology of high-purity tellurium. The main development direction of tellurium industry technology in the future is to optimize production process, improve product purity, reduce production energy consumption and improve recovery rate.
Specific methods for extracting tellurium
At present, there are two main methods to enrich tellurium from anode slime: alkali leaching and soda slagging. The method selected depends on the content of tellurium in anode slime, which cannot be generalized. When the tellurium content in anode mud is more than 2%, alkali leaching method is generally selected to improve the recovery rate of tellurium and avoid being dispersed in various minerals during anode mud treatment; When the content is less than 2%, soda slagging method is generally selected, and soda is added in the later stage of oxidation refining of silver separating furnace to enrich tellurium in soda slag for recovery.
The method of enriching tellurium by alkali leaching is to sulfuric the anode slime, bake and drag selenium, leach copper with water, and then leach tellurium with 10% caustic soda. When copper is removed by water leaching, copper sulfate dissolves into solution, tellurium is hydrolyzed into tellurium dioxide and remains in slag. The advantage of this method is that it is relatively non corrosive, has no volatile selenium loss, does not require cleaning or gas washing process, and can separate a large amount of selenium and tellurium. However, this method consumes a large amount of oxygen, because oxygen is consumed not only in the oxidation process of selenium and tellurium, but also in other components in the anode mud. The consumption of caustic soda is large. It not only converts lead sulfate in the anode mud into 4-valent lead acid, but also converts silicon dioxide in the anode mud into sodium silicate. In addition, almost all metal sulfates in anode slime are converted into sodium sulfate and corresponding oxides, hydroxides and sodium salts in the reaction process. Although there have been many studies on pressurized alkaline leaching, no factory has adopted this method so far due to various reasons.
The process is complex and the cost is too high
The process of recovering selenium and tellurium from anode slime containing selenium and tellurium by halometallurgy. The chlorinating agents used mainly include chlorides, hydrochloric acid and chlorides.
There are two chlorination methods: fire method and wet method. This is a practical method for comprehensively recovering selenium, tellurium and precious metals from anode slime containing selenium and tellurium. The pyrochlorination process is simple, and the volatilization rate of selenium and tellurium is up to 99%, but it requires high protection of equipment. The wet chlorination process is easy to control, easy to put into production, light pollution to the environment, the recovery rate of selenium and tellurium can also reach 98%~99%, and other valuable metals can be comprehensively recovered at the same time.
The Uses And Application Fields Of Tellurium
Application field development
Early tellurium applications were limited. During World War II, tellurium was used as a vulcanizing agent in the production of natural rubber. It was not until the late 1950s that tellurium became an element with industrial practical value. Tellurium and its compounds are widely used. Its downstream industries include solar energy, Alloy, thermoelectric refrigeration, electronics, rubber and other industries. The development of downstream industries directly determines the demand for tellurium. At present, the cadmium telluride thin film solar energy industry is developing rapidly and is considered to be one of the most promising solar energy technologies. It is expected that with the development of the cadmium telluride thin film solar energy industry, the demand for tellurium will continue to grow at a high speed.
Main products of tellurium
The main products of tellurium include metal tellurium, tellurium dioxide, tellurium powder and high-purity tellurium.
Distribution of Tellurium Applications
The application of tellurium in the metallurgical industry accounts for 42% of the total application. Due to the rapid development of tellurium in the photovoltaic field, the proportion of the metallurgical industry is declining.
Tellurium is mainly used as the alloy element of nonferrous metals and steel in the metallurgical industry. In the nonferrous metal industry, tellurium is used to improve the machinability of copper alloys. Adding tellurium to tin, Aluminum and lead based alloys can increase the hardness and plasticity of alloys. Adding tellurium to lead can be used to make cable sheaths, such as oil down the hole pumps. Adding 0.03% – 0.04% tellurium to cast iron and steel can reduce the nitrogen absorption of cast iron and steel, change the grain size of steel, and improve the strength and corrosion resistance of steel. Adding 0.001% – 0.002% tellurium to cast iron can make its surface strong and wear-resistant. Tellurium has an important influence on the microstructure, crystallization process, mechanical properties, etc. of cast iron, and its white tendency is the first among all elements. This tellurium treated steel has been used in mines, automation, railways and other equipment.
Tellurium powder used in chemical industry and rubber chemical industry accounts for about 21% of total tellurium application. In the chemical industry, tellurium and tellurium compounds can be used as additives for catalysts and dispersants in the rubber industry to improve the strength and elasticity of rubber.
Tellurium can play an important role in nickel electrolysis. Adding NaTeO3 (75ml/L) to the electrolyte can generate a transitional nickel layer, which can eventually form an electrolytic nickel layer with strong corrosion resistance. Tellurium catalysts have been used in petroleum cracking and coal hydrogenation. Tellurium can also prevent the oxidation of polymethylsiloxane. Tellurium is also used as a toner and solid lubricant in photography and printing industry. In addition, since the tellurium compound bismuth telluride has good refrigeration characteristics, it is also an ideal substitute for CFC-11 and CFC-12 (CFC-12 for short), which were originally used in the human refrigeration industry (refrigerators, air conditioners, etc.).
3.Electronic and electrical industry
Tellurium of infrared laser accounts for about 8% in the electronic and electrical industry. In the optoelectronic industry, semiconductor components ZnTe, CdTe, HgTe, HgCdTe, etc. are used for lasers, photodiodes, optical receivers, etc. involving infrared to ultraviolet spectra. The tellurides of lead, tin, mercury and cadmium are sensitive to infrared radiation. PbSnTe and CdHgTe compounds are important infrared photoelectric materials, and tellurium is an important raw material for the production of infrared materials.
Because SeTe and SeAs alloys have high photosensitivity per unit time, HgCdTe compounds are the main photosensitive materials used for infrared detectors in military and aerospace systems. Cadmium telluride (CdTe) is used in photoelectric systems because of its good light absorption characteristics. The high-purity tellurium used in the military in the United States reaches 99.9999%. With the excellent photosensitive properties of tellurium containing compounds, it has shown outstanding advantages in resource survey, satellite aerial survey, laser guidance, etc., and has been thoroughly demonstrated in the modern American war against Iraq. Tellurium is an important photoresist element in photographic plate making, laser printing and copying. It is the above-mentioned performance of tellurium in optoelectronics that plays an important role in the most attractive industry in the 21st century.
CdTe Thin Film Solar Cells
1. What is a cadmium telluride thin film solar cell?
Schematic diagram of the structure of cadmium telluride thin film solar cell CdTe thin film solar cell is referred to as CdTe cell, which is a thin film solar cell based on the heterojunction of p-type CdTe and n-type Cd. The general standard cadmium telluride thin film solar cell consists of five layers: back electrode, back contact layer, CdTe absorber layer, CdTe window layer, TCO layer. Current CdTe cells can be fabricated by a variety of methods, such as near-space sublimation, chemical bath deposition (CBD), screen printing, sputtering, evaporation, etc. The general industrialization and laboratory use the CBD method because the CBD method is low in cost and the generated CdS can form a good dense bond with TCO.
2. Global overview of cadmium telluride thin film solar cells
Global production companies include 5NPlus, Redlen and leading thin materials in Canada, of which 5NPlus is the world’s first manufacturer of cadmium telluride for thin-film solar energy that has achieved large-scale production, and is currently the world’s largest producer of cadmium telluride for thin-film solar energy. It has a large market share, and its scale has rapidly expanded with the growth of its main customer, First Solar. About 75% of the company’s sales revenue comes from First Solar. Redlen is one of the world’s leading manufacturers of radiation detectors and medical imaging equipment, and one of the few companies in the world with the production technology of cadmium telluride for thin-film solar power. The market share of cadmium products is not large. Leading Diluted Materials has been developing cadmium telluride for thin-film solar energy since 2006. It has passed the quality certification of some customers and has the technical capacity for large-scale production.
3. Development status and trend of domestic CdTe thin film solar cell industry
In the 1980s, the research work on CdTe thin film batteries in my country officially started. Initially, Inner Mongolia University used evaporation technology, Beijing Solar Energy Research Institute used electrodeposition technology (ED) to study and prepare CdTe thin film cells, and the latter developed cells with an efficiency of 5.8%. From the mid-1980s to the mid-1990s, research work was basically at a standstill, with little results. In the late 1990s, Professor Feng Lianghuan of the Institute of Solar Materials and Devices of Sichuan University led the research on cadmium telluride thin-film solar cells. Development of compound semiconductor polycrystalline thin-film solar cells”. The CdTe thin film battery was studied by near-space sublimation technology, and good results were obtained. Recently, the battery efficiency has exceeded 13.38%, entering the world’s advanced ranks. During the “Tenth Five-Year Plan” period, the research on CdTe thin film batteries was included in the “863” key project of the National High-Tech Research and Development Program.
After years of unremitting efforts of several generations of scientists, my country is in the stage of rapid development from laboratory basic research to application industrialization, and plans to establish a pilot production line with an annual output of 0.5MW. CdTe thin film solar cell research, from the original only Inner Mongolia University, Sichuan University, Xinjiang University and other research institutes to carry out basic research in this area, to this year’s Sichuan Apollo Solar Technology Development Co., Ltd. new thin film CdTe/CdS solar cell The industrialization of core materials will last for two years. It will build a production line with an annual output of 50 tons of cadmium telluride and a production line of 10 tons of cadmium sulfide, so that my country’s industrialization of CdTe thin-film solar cells will develop by leaps and bounds, and move towards the world’s leading level.
4. Problems and constraints
The production process of cadmium telluride thin-film solar cells is relatively easy, so its commercialization progresses faster than other thin-film solar cells. It has moved from the laboratory research stage to large-scale industrial production. At present, the next R&D focus of CdTe solar cells is how to further reduce costs, improve efficiency, and improve and perfect the production process. At present, the market share of CdTe batteries is not ideal. The reasons why it cannot be promoted to the mainstream of the market are as follows:
- The cost of module and substrate materials is too high. The overall CdTe solar cell material accounts for 53% of the total cost, of which semiconductor materials only account for about 5.5%.
- The natural reserves of tellurium are limited, and the total amount is bound to be unable to meet the needs of large and comprehensive reliance on such photovoltaic cells for power generation.
- The toxicity of cadmium makes people unable to accept such photovoltaic cells with confidence.
As a large-scale production and application of photovoltaic devices, CdTe solar cells have environmental pollution problems that cannot be ignored. The pollution of the toxic element cadmium (Cd) to the environment and the harm to the health of operators cannot be underestimated. We cannot obtain clean energy while causing new harm to the human body and the human living environment. Effectively disposing of discarded and broken CdTe components is not technically difficult. But cadmium is a highly toxic heavy metal, and its compounds are also toxic.
The main effects of cadmium:
- One is the harm caused by dust containing Cd to humans and other animals through the respiratory tract;
- The second is the ecological pollution caused by the discharge of production wastewater and waste.
Therefore, Cd and Te on broken glass sheets should be removed and recycled, damaged and discarded components should be properly disposed of, and waste water and waste discharged from production should be disposed of in accordance with environmental protection standards. At present, all countries are working to solve the factors that restrict the development of CdTe thin film solar cells.
Tellurium can also be used as a colorant for glass and ceramics, by adding tellurium-containing substances to produce different colors of glass and ceramics, and to make silverware, lead and brass surfaces a permanent beautiful black; adding tellurium Makes the enamel pink.
Compared with ordinary silicate glass, tellurium glass has the characteristics of high refractive index, low deformation temperature, high density and infrared transparency.
Glass containing a certain amount of germanium, sulfur and tellurium has good chemical properties in the infrared region, high mechanical strength, good heat resistance (softening point of 385°C) and thermal shock.
The infrared transparency of tellurium glass facilitates applications in infrared optics, such as infrared windows.
Good photosensitivity indicates that it can be used as a light-guide camera tube, and the low softening temperature makes it possible to make materials for vacuum-tight semiconductor elements.
Tellurium compounds have obvious anti-tumor effects, and also have the effect of inhibiting the proliferation of leukemia cells.
In addition, it can be used in pesticides, fungicides, in the production of radioisotopes, and in the treatment of hair loss, syphilis and other diseases. Studies have found that tellurium and its compounds are less toxic than selenium, water-soluble tellurium salts and tellurite salts are the most toxic, and elemental tellurium is the least toxic. For tellurium, the United Nations, the United States and some countries and organizations have proposed health-standard exposure threshold limits.
The Effect Of Tellurium On Human Health
Tellurium is a non-essential and cryptic trace element for human body. When the tellurium powder and vapor are inhaled by the human body, it will cause sweating disorders, causing the poisoned person to feel lethargic and vomiting, and have bad breath for several weeks, which is an obvious symptom of tellurium poisoning. The stench of sweat, urine, and breath is characteristic of tellurium poisoning. The maximum allowable concentration of tellurium in the air of the work area is 0.1 to 0.05 mg/m³. Compounds All tellurium compounds are almost toxic. The tellurium compounds with industrial value include oxides, sulfides, telluric acid and tellurite and halides.
Metabolism of tellurium in the human body
Sodium tellurite is easily absorbed by mammalian gastrointestinal tract and is mainly excreted in feces. Other tellurium compounds can be absorbed by skin, digestive tract or respiratory tract, and excreted in exhalation, sweat, urine and feces. Tellurium dioxide and tellurium salts are first reduced to elemental tellurium in the body, part of which is converted into dimethyl tellurium and diethyl tellurium and excreted in urine, feces and exhalation, and the other part is converted into dissolved state and excreted in urine and bile. After absorption, it can be combined with plasma proteins and distributed throughout the body. The content in kidney and blood is high. The content of tellurium in normal blood is 0.05%-0.16%, and the concentration of tellurium in urine and bile is 1 times that in blood. The content of tellurium in the organs shows a peak absorption at the end of 24 hours, and then decreases rapidly, and more than 80% is excreted in urine and feces within a few days. Since more than 95% of tellurium in the body is bound to proteins in various tissues, the excretion of tellurium is slow after several days. Tellurium mainly accumulates in the kidney, especially the renal cortex, followed by the liver, spleen, heart, lung and brain.
Overall, tellurium is less toxic than selenium. Acute toxicity in animals mainly damages the digestive system, central nervous system, cardiovascular and respiratory systems. Localized pneumonia and hemolytic anemia are typical features of acute tellurium toxicity, often accompanied by hematuria.
Chronic poisoning in animals is manifested as indigestion, growth arrest, weight loss, hair loss, exhalation garlic smell and lethargy.
The susceptibility of the population to tellurium varies greatly. Some people take 0.5mg TeO2 orally to cause breath garlic smell, and some people take 90mg of tellurium prescription to have this symptom. The concentration of tellurium in the air that does not cause the smell of garlic in the breath is 0.01~0.02mg/m3, and various symptoms can disappear on their own after the exposure.
- So far, for tellurium, the United Nations, the United States and other countries and organizations have proposed health-standard exposure limits.
- United States: The Short Time Exposure Limit (T LV – STEL) is 0.1 mg/m³.
- Occupational Safety and Health Administration (OSHA): Recommended Exposure Limit (REL-T WA) is 0.1 mg/m³.
- National Institute for Occupational Safety and Health (NI OSH): Recommended exposure limit (REL – TWA) of 0.1 mg/m³.
- Australia: Time-weighted average concentration (T WA ) of 0.1 mg/m³ (1990).
- Switzerland: T WA is 0.1mg/m³ (1990).
- UN: T WA is 0.1 mg/m³ (1991).
Tellurium Well-known Enterprises & Associations
China Well-known Enterprises
- Apollo Solar Energy, Inc
- Jiangxi Copper
- Guangdong Pilot Rare Materials Co., Ltd.
- Wonder Beryllium Copper Co., Ltd.
- Xiangtan County Churun Tellurium Co., Ltd.
- Gaoyao Zhonghe Metal Materials Factory
- Xingxian Jinrun Nonferrous Metals Co., Ltd.
Japan Well-known Enterprises
- Mitsui Materials Co., Ltd. (Kisan Kinzoku Chemicals Co., ltd.,)
- Mitsui Metal Mining and Smelting Co., Ltd.
- Nippon Rare Metals, Inc.
- mitsubishi materials Corp.,
- Pan Pan Pacific Copper Co., ltd.
- Shinko Chemicals Co., ltd.,
- Sumitomo metal mining Co., ltd.,