Chemical Properties
-325 mesh, 10μm or less 99.9% pure; occurs in nature as mineral scheelite; white tetr powder(s), a=0.524 nm, c=1.138 nm; can be prepared by heating tungstic acid and CaO or CaCO3; used in tumor treatment and in luminous paint [KIR83] [STR93] [MER06]
Large orange octahedral scheelite, Ca(WO4), crystal to 4.5 cm on muscovite, KAl2(AlSi3O10)(OH)2. Pingwu Co., Mianyang pref.,
Sichuan prov., China.
Uses
Calcium tungsten oxide is used as a luminophore.
Uses
Calcium tungstate can be ued for preparing screens for x-ray observations and photographs; in luminous paints; in scintillation counters.
Application
Calcium tungstate is well known as the phosphor that emits light in λ: 310–700 nm under the excitation light in λ: 220–300 nm. The peak wavelength is positioned at 440 nm, causing it to give off a blue color.
Production Methods
A single crystal is grown from melt by the Czochralski method. Rare earth ions are easy to incorporate into the crystal during growth. Fluorescent films are deposited on a glass substrate through vacuum evaporation using a W filament heated at 2000℃ for about 3 min, followed by thermal annealing in oxygen at 550℃ for 2 h. The film becomes crystalline through this thermal annealing.
General Description
Calcium tungstate (CaWO
4) is an optical material, which can be used as a laser host material for a variety of electronic applications. It has a scheelite structure with luminescence, and thermo-luminescence properties.
Structure and conformation
The space lattice of CaWO4 belongs to the tetragonal system, and its Scheelite structure has lattice constants of a=0.524 nm and c=1.138 nm. The space group is I4
1/a, and there are four formula units per unit cell.
