A rare-earth-free self-activated phosphor: Li2TiSiO5 with TiO5 square pyramids

To explore different photoluminescence phenomenon of Ti4+ ions, a rare-earth-free self-activated phosphor Li2TiSiO5 was synthesized and studied in detail. The crystal structure, photoluminescence properties and thermal quenching of Li2TiSiO5 were discussed. The crystal structure has been investigated by the Rietveld refinement, and it indicates that there is a special kind of TiO5 square pyramids in this structure. Under 245 nm excitation, Li2TiSiO5 emits white light ranging from 400 to 780 nm with CIE coordinates of (0.388, 0.441), which is due to the existence of isolated TiO5 square pyramids and TiO6 octahedron in the disordered non-crystalline powder, which is also proved by the time-resolved photoluminescence. The abnormal serious thermal quenching is ascribed to thermal ionization. The study of Li2TiSiO5 broadens the research of rare-earth-free Ti-doped oxides due to its self-activated luminescence and the realization of white light emission in a single host.