Role of chemical substitution in the photoluminescence properties of cerium samarium tungstates Ce(2-x)Smx(WO4)3 (0≤x≤0.3)

A series of cerium samarium tungstates Ce(2– x )Sm x (WO4)3 with $x \le 0.3$ was synthesized by a coprecipitation method followed by thermal treatment at 1000 °C. The polycrystalline compounds were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) experiments. Using the Rietveld procedure, the decrease in cell parameters showed that a solid solution was obtained. A comparative analysis of diffraction profiles allowed determining structural distortions increasing with increasing composition $x$ . The PL experiments were performed under UV and XR excitations. The variations with composition $x$ of emission intensities observed in the wavelength range of 500–1000 nm, corresponding to complex charge transfers (CTs) and quenching effects, were interpreted in terms of transitions proper to Ce3+ and Sm3+ cations, accompanied by additional transitions due to oxygen vacancies and other point defects due to substitution and synthesis conditions.