Photoluminescence Studies and Core–Shell Model Approach for Rare Earthdoped CdWO₄ Nano Phosphor

Abstract

The present paper reports synthesis and photoluminescence studies of Cadmium tungstate (CdWO₄) and Cerium doped CdWO₄. The phosphor samples were synthesized by low cost and low temperature hydrothermal method. The received materials are characterized by XRD, FTIR, TEM and photoluminescence (PL) studies are reported. XRD pattern reveals that the CdWO₄ has monoclinic wolframite structure and the shift toward higher angle of reflection peaks suggests that the cell parameters of as-synthesized phosphor could continuously decreases and also crystallite size decreases when the Ce concentration increases. The FTIR spectrum of Cerium doped CdWO₄ exhibits intrinsic bending (Cd-O) and stretching vibrations (W-O). When the pH is varied from 4 to 8 the formation of nano spheres (4 pH) nano rods (6 pH) and agglomeration as well as nano tubes (8 pH) are observed which are confirmed from TEM studies. This may be due to that formation of nano material and also the change in nature of aqueous solution from acidic to basic. When the pH changed from acidic to basic while preparing the materials the observed PL emission in the synthesized phosphor the PL intensity increases. From PL studies it suggests that more radiative traps are responsible in basic medium when compare to acidic solution and 7 nm shift in PL emission spectra observed (blue to violet region) may be due the formation of nano phosphor.