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| Zinc oxide | |
|---|---|
| General | |
| Other names | Zinc white, calamine |
| Molecular formula | ZnO |
| Molar mass | 81.41 g/mol |
| Appearance | White solid |
| Crystal Structure | cubic |
| CAS number | |
| Properties | |
| Density and phase | 5.606 g/cm3, solid |
| Solubility in water | Insoluble |
| Melting point | 1975°C (decomposes) |
| Boiling point | |
| Mohs hardness | 5 |
| a Lattice constant | 4.63Å |
| Thermodynamic data | |
| Standard enthalpy of | formation]] ΔfH°solid
−348.0 kJ/mol |
| Standard molar entropy S°solid | 43.9 J.K−1.mol−1 |
| Hazards | |
| EU classification | Dangerous for the environment (N) |
| R-phrases | , , . |
| S-phrases | , . |
| NFPA 704 | nfpa_f0.pngnfpa_r0.png|
| Supplementary data page | |
| Structure and properties | n, εr, etc. |
| Thermodynamic data | Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Regulatory data | Flash point, RTECS number, etc. |
| Related compounds | |
| Other anions | Zinc sulfide Zinc selenide Zinc telluride |
| Other cations | Cadmium oxide Mercury oxide |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Chemical infobox | |
Zinc oxide is a chemical compound with formula ZnO. It is nearly insoluble in water but soluble in acids or alkalis. It occurs as white hexagonal crystals or a white powder commonly known as zinc white. It remains white when exposed to hydrogen sulfide or ultraviolet light. Crystalline zinc oxide exhibits the piezoelectric effect, is luminescent (it will change colour from white to yellow when heated, and back again when cooled down), and is light sensitive. Zinc oxide decomposes into zinc vapor and oxygen at around 1975°C.
Zinc oxide occurs in nature as the mineral zincite.
Applications
Zinc peroxide, ZnO2 .½ H2O, is a white to yellow powder used in antiseptic ointments, like Calamine Lotion.
Zinc white is used as a pigment in paints and is less opaque than lithopone, but more transparent than titanium dioxide. It is also used in coatings for paper. Chinese white is a special grade of zinc white used in artists' pigments. Because it absorbs both UVA and UVB rays of ultraviolet light, zinc oxide can be used in ointments, creams, and lotions to protect against sunburn and other damage to the skin caused by ultraviolet light.
Zinc oxide and stearic acid are important ingredients in the commercial manufacture of rubber goods. A proper mixture of these two compounds allows a quicker and more controllable rubber cure. Zinc oxide can also be used as a filler in some rubber mixtures.
Zinc oxide is a semiconductor with a direct band gap of 3.2 eV (387 nm, deep violet/borderline UV). A common application is in gas sensors. As of 2003, it has been utilized in recent research to build blue LEDs and transparent TFTs.
N-type doped films are often used in thin film technology, where zinc oxide serves as a TCO (transparent conducting oxide). N-type doping is possible by introduction of hydrogen or zinc interstitial defects. oxygen vacancies are no longer considered to contribute to the n-type conductivity because these levels are too deep in the band gap. P-type doping is difficult and is currently an active area of research. Thin-film solar cells, LCD and flat panel displays are typical applications of this material. Zinc oxide is transparent and conductive, and can therefore be used as a transparent electrode. Indium tin oxide (ITO) is another transparent conducting oxide often used in microelectronics.
ZnO has also been considered for spintronics applications because of theoretical predictions of room temperature ferromagnetism. Unsubstantiated reports of ferromagnetism have been reported, but presence of dilute magnetic semiconductors remains a large unanswered question in physics.
ZnO layers are mainly deposited by sputtering and chemical vapor deposition (CVD). The latter method allows the growth of a rough layer, which can diffuse the incoming light by scattering, increasing the efficiency of solar cells.
Pyroelectric coefficient
- Primary pyroelectric coefficient: -6.8 μC/m2·K
- Secondary pyroelectric coefficient: -2.5 μC/m2·K
- Total pyroelectric coefficient: -9.4 μC/m2·K
External links
- International Chemical Safety Card 0208.
- NIOSH Pocket Guide to Chemical Hazards.
- Nav Bharat Metallic Oxide Industries. (uses of zinc oxide)
- External MSDS Data Sheet.
References
- Physics Today, volume 58, No. 8, p.33, August 2005.
Oxides | Zinc compounds | Inorganic pigments | Inorganic compounds | Semiconductor materials
Цинков оксид | Zinkoxid | Óxido de zinc | Cinko baltalas | Zinkoxide | 酸化亜鉛 | Оксид цинка | 氧化鋅
"Zinc oxide"
