Systematic study of photoluminescence, lyoluminescence and mechanoluminescence in Ce3+ - and Eu3+ -activated Li3 PO4 phosphors.

Li3 PO4 phosphor was prepared using a modified solid-state diffusion technique. In this work, photoluminescence, lyoluminescence and mechanoluminescence studies were carried out in a Li3 PO4 microcrystalline powder doped with different rare earths. In photoluminescence studies, characteristic emission of Ce and Eu was observed. The lyoluminescence glow curves of Li3 PO4 microcrystals show that lyoluminescence intensity initially increases with time and then decreases exponentially. The decay time consists of two components for all masses. The dependence of decay time, especially the longer component, on mass has been investigated. Experiments on γ-irradiated crystals have proved that the light emission originates from the recombination of released F-centres with trapped holes (V2-centres) at the sulfuric acid-solid interface. Incorporation of bivalent alkali in solid lithium phosphate leads to an enhancement of lyoluminescence. A possible explanation for the experimental results has been attempted. The phosphor has a mechanoluminescence single glow peak. Mechanoluminescence intensity under various loading conditions was investigated. It is observed that mechanoluminescence intensity increases with increasing impurity concentration and increasing piston impact velocity. The results may be considered as only being of academic interest in solid-state materials.