Photoluminescent properties of fresnoite phosphors prepared from phase-separated BaO-TiO₂-SiO₂ glasses

Abstract

Glass ceramic phosphors containing fresnoite (Ba₂TiSi₂O₈) were prepared from glasses both within and outside the immiscibility region of the BaO-TiO₂-SiO₂ system by conventional melt-quenching and subsequent heat treatment. The phosphors showed blue-white photoluminescence (PL) under ultraviolet excitation, and the effects of the crystalline phase precipitated and the fine structure of the ceramics on their PL properties were examined. Phase-separated textures were observed in the samples with compositions within the immiscibility region. The predominant crystalline phase precipitated in the heat-treated sample was fresnoite. Sample PL intensity was related not only to the amount of precipitated fresnoite, but also to the microstructure of the sample resulting from phase separation. The highest PL intensity was obtained from a 22BaO·11TiO₂·67SiO₂ sample from the immiscibility region, because of the formation of an appropriate fine glass-ceramic structure for photo-excitation of fresnoite.