Zinc Oxide 500g
Zinc Oxide 500g
ZnO
Zinc oxide is an inorganic compound with the formula ZnO. ZnO is a white powder that is insoluble in water. It is used as an additive in numerous materials and products including cosmetics, food supplements, rubbers, plastics, ceramics, glass, cement, lubricants,[10] paints, ointments, adhesives, sealants, pigments, foods, batteries, ferrites, fire retardants, and first-aid tapes. Although it occurs naturally as the mineral zincite, most zinc oxide is produced synthetically.[11]
ZnO is a wide-band gap semiconductor of the II-VI semiconductor group. The native doping of the semiconductor due to oxygen vacancies or zinc interstitials is n-type.[12] Other favorable properties include good transparency, high electron mobility, wide band gap, and strong room-temperature luminescence. Those properties make ZnO valuable for a variety of emerging applications: transparent electrodes in liquid crystal displays, energy-saving or heat-protecting windows, and electronics as thin-film transistors and light-emitting diodes.
Chemical Properties
Properties | |
---|---|
ZnO | |
Molar mass | 81.406 g/mol[1] |
Appearance | White solid[1] |
Odor | Odorless |
Density | 5.606 g/cm3[1] |
Melting point | 1,974 °C (3,585 °F; 2,247 K) (decomposes)[1][5] |
Boiling point | 1,974 °C (3,585 °F; 2,247 K) (decomposes) |
0.0004% (17.8°C)[2] | |
Band gap | 3.3 eV (direct) |
−27.2·10−6 cm3/mol[3] | |
Refractive index (nD) | n1=2.013, n2=2.029[4] |
Safety Zinc Oxide 500g
Dangerous for environment
Keep it in cool and dry place at r.t.
Descriprion
Chemical properties
Pure ZnO is a white powder, but in nature it occurs as the rare mineral zincite, which usually contains manganese and other impurities that confer a yellow to red color.[13]
Crystalline zinc oxide is thermochromic, changing from white to yellow when heated in air and reverting to white on cooling.[14] This color change is caused by a small loss of oxygen to the environment at high temperatures to form the non-stoichiometric Zn1+xO, where at 800 °C, x = 0.00007.[14]
Zinc oxide is an amphoteric oxide. It is nearly insoluble in water, but it will dissolve in most acids, such as hydrochloric acid:[15]
- ZnO + 2 HCl → ZnCl2 + H2O
Solid zinc oxide will also dissolve in alkalis to give soluble zincates:
- ZnO + 2 NaOH + H2O → Na2[Zn(OH)4]
ZnO reacts slowly with fatty acids in oils to produce the corresponding carboxylates, such as oleate or stearate. ZnO forms cement-like products when mixed with a strong aqueous solution of zinc chloride and these are best described as zinc hydroxy chlorides.[16] This cement was used in dentistry.
Physical properties Zinc Oxide 500g
Structure
Zinc oxide crystallizes in two main forms, hexagonal wurtzite[19] and cubic zincblende. The wurtzite structure is most stable at ambient conditions and thus most common. The zincblende form can be stabilized by growing ZnO on substrates with cubic lattice structure. In both cases, the zinc and oxide centers are tetrahedral, the most characteristic geometry for Zn(II). ZnO converts to the rocksalt motif at relatively high pressures about 10 GPa.[12] The many remarkable medical properties of creams containing ZnO can be explained by its elastic softness, which is characteristic of tetrahedral coordinated binary compounds close to the transition to octahedral structures.[20]
Hexagonal and zincblende polymorphs have no inversion symmetry (reflection of a crystal relative to any given point does not transform it into itself). This and other lattice symmetry properties result in piezoelectricity of the hexagonal and zincblende ZnO, and pyroelectricity of hexagonal ZnO.