Bi3+ - doped garnets as possible ultraviolet persistent phosphors

Ultraviolet (UV) persistent luminescence (afterglow) and thermally stimulated luminescence observed in the 3.6–4.2 eV energy range are studied for microcrystalline powders of the Bi3+-doped Lu3Ga5O12, Y3Ga5O12, and Ca3Ga2Ge3O12 garnets after their selective UV irradiation at 295 K in the 4–6 eV energy range. Emission and excitation spectra and decay kinetics of the persistent luminescence, as well as the luminescence intensity dependence on the irradiation duration, are measured at 295 K. No UV emission has been observed in the afterglow spectrum of the Gd3Ga5O12:Bi, Lu3Al5O12:Bi, and Y3Al5O12:Bi garnets. The processes resulting in the appearance of the UV persistent luminescence in the investigated Bi3+-doped garnets are discussed. The conditions are formulated which ensure the appearance of this phenomenon in Bi3+-doped compounds and, thus, could inspire the discovery of new effective UV persistent phosphors.