Variable properties of solid solutions of cerium-samarium tungstates Ce(2-x)Smx (WO4)3 (x≤0.3)

A solid solution Ce(2-x)Sm x(WO4)3 with x≤0.3 was synthesized via a coprecipitation route followed by thermal treatment at 1000 °C. The polycrystalline compounds were characterized by X-ray diffraction, scanning electron microscopy and photoluminescence experiments. Using Rietveld procedure, the decrease of cell parameters showed that a solid solution was obtained. A comparative analysis of diffraction profiles allowed determining structural distortions increasing with composition x. Photoluminescence (PL) experiments were performed under UV and X-ray excitations. The variations with composition x of PL emission intensities, corresponding to complex charge transfers and quenching effects, were interpreted in terms of transitions proper to Ce3+ and Sm3+ cations, accompanied by additional transitions probably due to oxygen vacancies and other point defects generated by substitution and synthesis conditions. The CIE chromaticity diagrams showed variable colors located in the orange-red range.