telluroxocadmium
Cadmium telluride
CAS: 1306-25-8
Molecular Formula: CdTe
telluroxocadmium - Names and Identifiers
| Name | Cadmium telluride |
| Synonyms | irtran6 telluroxocadmium Cadmium telluride CADMIUM TELLURIDE cadmiummonotelluride cadmiumtelluride(cdte) Cadmium telluride, powder, Cadmiumtelluridemetalsbasisblacklumps Cadmium telluride Coating quality Balzers |
| CAS | 1306-25-8 |
| EINECS | 215-149-9 |
| InChI | InChI=1/Cd.Te/rCdTe/c1-2 |
telluroxocadmium - Physico-chemical Properties
| Molecular Formula | CdTe |
| Molar Mass | 240.01 |
| Density | 6.2 g/mL at 25 °C (lit.) |
| Melting Point | 1092 °C |
| Boling Point | 1130°C |
| Water Solubility | Insoluble in water. |
| Vapor Presure | 0Pa at 25℃ |
| Appearance | crystalline |
| Specific Gravity | 6.2 |
| Color | Black |
| Exposure Limit | ACGIH: TWA 0.01 mg/m3; TWA 0.002 mg/m3; TWA 0.1 mg/m3NIOSH: IDLH 9 mg/m3; IDLH 25 mg/m3; TWA 0.1 mg/m3 |
| Merck | 14,1629 |
| Refractive Index | 2.75 |
| Physical and Chemical Properties | Chemical formula CdTe. Molecular weight 240.00. Black cubic crystals. Toxic! Melting point of 1041 deg C, higher temperature decomposition, the relative density of 6.2015. Insoluble in water, acid, but with nitric acid and decomposition. It is easily oxidized by air when wet. Preparation Method: The mixture of tellurium and cadmium is melted, sublimated in hydrogen flow, or cadmium tellurite or tellurite is reduced by heating in hydrogen flow, it can also act on sodium telluride and Cadmium acetate solution acidified by acetic acid. When precipitated from the solution, it is brown-red and almost turns black after drying, the formation of cadmium telluride single crystal. |
telluroxocadmium - Risk and Safety
| Risk Codes | R45 - May cause cancer R20/21/22 - Harmful by inhalation, in contact with skin and if swallowed. R50/53 - Very toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment. |
| Safety Description | S53 - Avoid exposure - obtain special instructions before use. S22 - Do not breathe dust. S61 - Avoid release to the environment. Refer to special instructions / safety data sheets. S60 - This material and its container must be disposed of as hazardous waste. |
| UN IDs | UN 2570 6.1/PG 3 |
| WGK Germany | 3 |
| RTECS | EV3330000 |
| TSCA | Yes |
| HS Code | 28429090 |
| Hazard Class | 6.1(b) |
| Packing Group | III |
telluroxocadmium - Reference Information
| crystal structure | Hexagonal, Wurtzite (Zincite) Structure - Space Group P 63mc |
| EPA chemical information | Information provided by: ofmpub.epa.gov (external link) |
| semiconductor material | cadmium telluride is an important group II-VI compound semiconductor material composed of tellurium and cadmium. The molecular formula is CdTe, its crystal structure is sphalerite type, with direct transition energy band structure, lattice constant 0.6481nm, melting point 1092 ℃, density 5.766g/cm3, forbidden band width 1.5eV(25 ℃), energy band structure is direct type, electron mobility (25 ℃) 1050 cm2/(V s), hole mobility (25 ℃) 80 cm2/(V s), electron effective mass 0.096, resistivity 103~107 Ω · cm. Using high-purity tellurium and cadmium as raw materials, cadmium telluride is synthesized after deoxidation, and then grown into single crystal or polycrystalline by vertical directional crystallization or vertical zone melting. Single crystal is used to make infrared electro-optic modulators, infrared detectors, infrared lenses and windows, phosphors, normal temperature gamma-ray detectors, solar cells and light-emitting devices close to the visible light region, etc., cadmium telluride solar cells, compared with monocrystalline silicon Solar cells have the advantages of convenient production, low cost and light weight. Ⅱ-Ⅵ compound semiconductor materials are important semiconductor materials with high and poor mechanical properties. So far, it is difficult to make large-diameter single crystals, and many materials are mostly made into epitaxial films. Important applications include cadmium telluride, cadmium sulfide, zinc selenide, zinc sulfide, and mercury cadmium telluride (Hg1-xCdxTe), a solid solution semiconductor material of this family. |
| Polycrystalline cadmium telluride synthesis | The main structural defect of cadmium telluride is the interstitial cadmium atom, which provides n-type conductance, while cadmium vacancies provide p-type conductance. Weigh with tellurium and cadmium with purity of 99.9999% according to the element mass ratio of 1:1, and put the material into a carbon-coated quartz tube, deoxidizing the material under a vacuum degree of less than 4 × 10-4Pa, and then seal the quartz tube under a vacuum degree of less than 2 × 10-4Pa. Then the sealed quartz tube is put into the synthesis furnace for polycrystalline cadmium telluride synthesis. In order to prevent the rapid evaporation of cadmium during synthesis from causing the explosion of the tube, the temperature rise must be carried out slowly, because at the melting point of cadmium telluride, the vapor pressure of cadmium is 1MPa. When the temperature rises to 800 ℃, the temperature is kept constant for 4h, then slowly rises to 1100 ℃, and the whole synthesis time is 14h. |
| single crystal cadmium telluride growth | the synthesized polycrystalline material can be grown by vertical brychmann method, tellurium flux method, gas phase sublimation method, high pressure melt growth method, etc. The growth rates were 2mm/h, 3mm/h, 0.2 mm/h and 5mm/h respectively. The vertical Brichmann method is now commonly used to grow cadmium telluride single crystals, and its growth diagram is shown in the figure. Schematic diagram of the growth of cadmium telluride single crystal 1-transmission mechanism; 2-quartz ampoule; 3-multi-stage resistance furnace; 4-cadmium source; 5-cadmium telluride polycrystalline material; 6-Growth of cadmium telluride single crystal It is difficult to grow cadmium telluride single crystal. The reason is that the element cadmium and the element telluride have higher vapor pressure at the growth temperature of cadmium telluride, so the crystal is easy to deviate from the chemical ratio; another reason is that cadmium is easy to stick to quartz ampoules. Internationally, crystals with less than three grains on the crystal section are called single crystals. Cadmium telluride single crystal can be used for infrared electro-optic modulators, infrared detectors, HgCdTe substrate materials, infrared windows, room temperature X-ray detectors, solar cells, and light-emitting devices close to the visible region. |
| Mercury cadmium telluride | Mercury cadmium telluride (CdxHg1-xTe) is a ternary solid solution semiconductor composed of Ⅱ-Ⅵ compounds cadmium telluride and mercury telluride. It is a narrow-band semiconductor material. With the change of component x, the forbidden band width and other energy band parameters also change. The band gap Eg varies with temperature t and component x with the following empirical formula: Eg (t x)= 0.30 5 × 10-4T (1.91-10-3T)x. Narrow-band semiconductors are generally energy-band inversion semiconductors. For Cdx and Hg1-xTe, at low temperatures, when the x value is small, it is a semi-metal or semiconductor with zero forbidden band width. When x increases to a certain value, the CdxHg1-xTe changes from semi-metal to narrow-band semiconductor, resulting in energy band inversion (77K,x = 0.15). At this time, the effective mass of electrons becomes smaller and the electron mobility increases, thus causing many changes in physical properties. The infrared detector made of mercury cadmium telluride has good characteristics, especially in the vicinity of the atmospheric window with a wavelength of 8~14 μm, and its sensitivity is very high, so it has been developed rapidly as a good laser receiving material. Since mercury cadmium telluride is composed of compounds of group II-VI with a higher melting point. At high temperatures, the vapor pressures of cadmium, mercury, and tellurium are all very high, so the mercury cadmium telluride crystals grown from the melt often produce serious components Deviations affect the performance of materials and devices, so improve the preparation method of mercury cadmium telluride, improving the quality of its single crystal is still an important research topic. Reference: Feng Duan Editor-in-Chief. A dictionary of solid state physics. Beijing: Higher Education Press. 1995. Page 213. |
| use | spectral analysis. It is also used to make solar cells, infrared modulators, HgxCdl-xTe substrates, infrared window electroluminescent devices, photovoltaic cells, infrared detection, X-ray detection, nuclear radioactivity detectors, light emitting devices close to the visible light region, etc. |
| production method | 1. Tellurium and cadmium are mixed in a stoichiometric ratio and directly combined at high temperature. 2. Pass hydrogen telluride gas into cadmium salt solution to make it precipitate. CdTe products can be obtained by suction filtration, washing and drying. |
| category | toxic substances |
| toxicity classification | poisoning |
| acute toxicity | abdominal injection-rat LD50: 2820 mg/kg; Abdominal injection-mouse LD50: 2100 mg/kg |
| flammability hazard characteristics | when exposed to acid, moisture, or high heat, it emits highly toxic cadmium and telluride gas |
| storage and transportation characteristics | warehouse ventilation and low temperature drying; Separate storage and transportation from acids and food |
| fire extinguishing agent | water, sand |
| occupational standard | TLV-TWA 0.05 mg (cadmium)/m3; STEL 0.1 mg (cadmium)/m3 |
Last Update：2024-09-04 09:30:31
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