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

Abstract

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 Rietveld refinement, and this 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 octahedra 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.