Structural characterization of Li2(MgxZn1−x)2W2O9 for bluish-white luminescence in rare earth-free tungstate phosphors

Abstract

Self-activated phosphors have attracted considerable attention due to their low synthesis temperature, high excitation threshold, and broad emission spectrum. And self-activated tungstate phosphors are distinguished by their low cost and stable chemical properties. Generally, it is difficult to observe luminescence from tungstate phosphors at room temperature. Furthermore, blue-emitting tungstate phosphors with high quantum efficiency are rarely reported. In this study, we succeeded in discovering high quantum-efficiency bluish-white-emitting Li₂(Mg_xZn_1−x)₂W₂O₉ phosphors and investigating their detailed crystal structures. Upon near-ultraviolet excitation at 266 nm, these phosphors exhibit a broadband emission peak. The red shift of emission is slight with increasing Zn content in Li₂(Mg_xZn_1−x)₂W₂O₉. A highly compact octahedral [WO₆] unit is observed in the Li₂(Mg_xZn_1−x)₂W₂O₉ phosphors. The phosphors exhibit high internal quantum efficiencies (IQEs) of 68.70% (M = Mg), 43.90% (M = Mg_0.5Zn_0.5), and 22.90% (M = Zn), respectively. This study provides a bluish-white-emitting tungstate phosphor with high quantum efficiency.