Lanthanide ion induced phase decomposition of tetragonal CaWO4

Abstract Undoped and europium (Eu3+) doped CaWO4 samples were prepared at room temperature using co-precipitation method and investigated for their thermal stability by annealing at different temperatures, namely 300, 500, 700 and 900 °C in air. It is observed that incorporation of Eu3+ ions destabilizes CaWO4 lattice and favors its decomposition at elevated temperatures. Powder X-ray diffraction (XRD) studies confirmed that as-synthesized CaWO4: 1% Eu3+ remains stable up to an annealing temperature of 500 °C, and above that it partially decomposes into WO3 phase. Unlike this, undoped CaWO4 remains stable under similar annealing conditions. Photoluminescence, UV–Visible, and infra-red absorption studies provide important evidence for partial decomposition of CaWO4: 1% Eu3+ into its constituent oxides upon annealing at temperatures above 500 °C.