Blue photoluminescence, greenish-blue afterglow and their Ti-concentration dependence in rare earth-free bazirite-type BaZr_1-xTi _xSi₃0₉

We synthesized Ti-bearing bazirite (BaZr_1-xTi_xSi ₃O₉), x=0-0.2) and examined their spectroscopic features comprehensively, in order to elucidate the photoluminescent properties in the bazirite phase. Strong emission around 2.79 eV was observed in the synthetic bazirite phase with x=0.01 by UV excitation, which exhibited an internal quantum yield of 72% at room temperature. In addition, the bazirite phases also showed clear afterglow with peak around 2.62 eV in the range of x=0.005-0.03, whereas no afterglow property was confirmed in Ti-bearing pabstite (BaSnSi ₃0₉) phases, in spite of being isostructural of bazirite. It was demonstrated that presence of Zr- related center is a necessary condition for evolution of the afterglow property in the bazirite structure.