Thermal and luminescent properties of M2Zn(VO3)4 (M = Rb, Cs)

Abstract

We have developed processes for the synthesis of the Rb2Zn(VO3)4 and Cs2Zn(VO3)4 tetrametavanadates. Rb2Zn(VO3)4 has been prepared by solid-state reaction (350°C) between presynthesized RbVO3 and ZnV2O6 powders, and Cs2Zn(VO3)4 has been prepared by the Pechini method (sol-gel process). Both metavanadates crystallize in monoclinic symmetry (sp. gr. P21/m). Thermochemical characterization results demonstrate that the vanadates undergo complex transformations during heating to 450°C and subsequent cooling. As a result, the materials are in a nonequilibrium state at room temperature and consist of both the parent double metavanadates and their peritectic decomposition products. We believe that the formation of the structure of the M2Zn(VO3)4 compounds from their melts is a kinetically hindered process. These compounds are structurally stable only at temperatures below 369 (Rb2Zn(VO3)4) or 420°C (Cs2Zn(VO3)4). We have measured for the first time the diffuse reflectance and photoluminescence excitation spectra of the two tetrametavanadates in their emission range and their photoluminescence spectra at various excitation wavelengths and determined their chromaticity coordinates. Their X-ray luminescence and scintillation decay characteristics have been determined for the first time under pulsed electron beam excitation. The electron excitation dissipation processes in the cesium and rubidium compounds are shown to be similar. We discuss the origin of the emission bands in the mixed vanadates and their potential application areas.