Structural, vibrational and luminescence properties of solid solution based on the (1-x/2) Ce2(WO4)3 + (x/2) Sm2(WO4)3 system

Abstract

A series of 14 polycrystalline cerium samarium tungstates belonging to the system [(1-x/2).Ce2(WO4)3 + x/2 Sm2(WO4)3] was synthesized by a coprecipitation method followed by thermal treatment at 1000 °C. The polycrystalline samples were characterized by X-ray diffraction, scanning electron microscopy and Raman spectroscopy. Their crystal structure was subjected to Rietveld refinement calculations and quasi-linear variation of cell parameters was observed, suggesting the formation of a solid solution Ce(2-x)Smx(WO4)3 (0 ≤ x ≤ 2). Raman spectroscopy was used to confirm the formation of the disordered solid solution. The analyses of Bragg peak and Raman emission profiles allowed evidencing the formation of structural defects. Scanning electron microscopy images show relatively well crystallized grains. Photoluminescence experiments were performed under polychromatic X-ray excitation delivered by copper source. The characteristic luminescence of Ce3+ cations was not observed whatever the composition x. The resulting emissions were ascribed to Sm3+ cations associated with additional emission from structural defects. Chromaticity diagrams show that color coordinates vary with Sm composition and structural defects in the orange-red range.