Zinc oxide

Zinc oxide is a chemical compound with formula ZnO, that 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, and is light sensitive.

Zinc oxide occurs in nature as the mineral zincite. Zinc peroxide, ZnO₂ .½ H₂O, is a white to yellow powder used in antiseptic ointments.

Zinc white is used as a pigment in paints; less opaque than lithopone. It is also used as a filler for rubber goods and in coatings for paper. Chinese white is a special grade of zinc white used in artists' pigments. Because it absorbs ultraviolet light, zinc oxide can be used in ointments, creams, and lotions to protect against sunburn.

Zinc oxide is a semiconductor with a direct band gap of 3.2eV. A common application is in gas sensors. As of 2003, it has been utilized in recent research to build blue LEDs and transparent TFTs.