Spectroscopic and luminescence studies of Cr3+ doped cadmium silicate nano-phosphor

CdSiO3:Cr3+ (1-9 mol%) nanophosphor was synthesized by a low temperature solution combustion technique. The final products were well characterized by powder X-ray diffraction (PXRD), scanning electron microscopy, transmission electron microscopy as well as Fourier transform infra-red, Raman and UV-visible spectroscopies. The PXRD results revealed that the samples were well crystallized with monoclinic phase. The average crystallite sizes estimated by Scherrer׳s method, Williamson-Hall (W-H) plots and size-strain plot were found to be in the range of 20-45 nm. The energy band gap of the phosphors was found to be in the range of 5.42-5.47 eV. Photoluminescence studies show an intense emission peak at 691 nm for the excitation wavelength of 361 nm, which corresponds to 2Eg→4A2g transition of R-line of chromium. Racah parameters were estimated to describe the effects of electron-electron repulsion within the crystal lattice. It was observed that PL intensity increases with increase in Cr3+ concentration. The highest PL intensity was observed from 7 mol% doped sample and thereafter, it decreases with further increase in Cr3+ concentration; this may be due to cross relaxation leading to a concentration quenching. The chromaticity co-ordinates and correlated color temperature of all the phosphors were well located in red region, which is a high potential for the fabrication of red component of white light emiting diodes (WLEDs).