Structure and luminescent properties of LaNbO4 synthesized by sol-gel process

The luminescence properties of LaNbO4 synthesized by the citric gel process were investigated. The crystallized orthorhombic and monoclinic biphasic structure forms at temperatures below 1100 °C and well-crystallized monoclinic LaNbO4 is obtained by heat treatment at a temperature of 1200 °C for 3 h. All of LaNbO4 phosphors derived from the citric gel method exhibit red-shifted excitation spectra as the calcining temperature increased from 700 to 1200 °C. The effect of the heat treatment conditions on the peak shape and the peak positions of the photoluminescence (PL) emission are undetectable, and the PL spectra excited at 260 nm have a blue emission band maximum at 408 nm, corresponding to the self-activated luminescence center of LaNbO4. The sample heat treated at 1100 °C for 3 h showed the highest absorption and fluorescence intensities among the prepared samples.