Structural, vibrational and luminescence properties of the (1−x)CaWO4−xCdWO4 system

• Solid solutions Ca1−xCdxWO4 are elaborated from coprecipitation technique.
• The structures of two types of solid solutions are refined using Rietveld method.
• A maximum of luminescence is obtained for an intermediate composition x=0.8.

In the present work, we investigate the structural, microstructural, vibrational and luminescence properties of the system (1−x)CaWO4−xCdWO4 with x ranging between 0 and 1. Polycrystalline samples were elaborated using a coprecipitation technique followed by thermal treatment at 1000 °C. The samples were then characterized using X-ray diffraction, scanning electron microscopy, Raman spectroscopy and luminescence analyses. X-ray diffraction profile analyses using Rietveld method showed that two kinds of solid solutions Ca1−xCdxWO4 having scheelite and wolframite structures, with respectively tetragonal and monoclinic crystal cells, were observed, with a biphasic system for compositions x=0.6 and 0.7. The scanning electron microscopy experiments showed a complex evolution of morphologies and crystallite sizes as x increased. The vibration modes of Raman spectra were characteristic of composition-dependent disordered solid solutions with decreasing wavenumbers as x increased. Luminescence experiments were performed under UV-laser light irradiation. The energies of emission bands increased linearly with cadmium composition x. The integrated intensity of luminescence reached a maximum value for the substituted wolframite phase with composition x=0.8.

Luminescence on UV excitation (364.5 nm) of (1−x)CaWO4−xCdWO4 system, elaborated from coprecipitation technique at 1000 °C, with 0