Mixed vanadates: Optimization of optical properties by varying chemical composition

Mixed LuxY1-xVO4 crystals, undoped and doped with Eu3+, were synthetized by the solid state reaction method. The crystal structure and phase composition were controlled by the X-ray diffraction (XRD), Raman analysis, and scanning electron microscope (SEM) measurements. The samples' crystallinity was improved by annealing. Nevertheless, the lattice distortion caused by the substitution of Y by Lu was detected. The lattice parameters derived from the XRD data are in good agreement with the calculated ones. It was found that the luminescence intensity increase in the annealed samples is related to the improvement of crystallinity of samples. According to the studies of X-ray excited luminescence at 300 K the relative luminescence intensity increases for the samples with intermediate values of x. For the LuxY1-xVO4:Eu3+ the highest luminescence intensity was detected for x=0.7 and ascribed to the effect of decrease of the mean distance between the thermalized electrons and holes. For the undoped crystals the luminescence is partially quenched at 300 K, however the sample with x=0.7 demonstrate highest intensity as well. The effect in the undoped samples is due to the increase of the temperature of luminescence quenching in samples with intermediate values of x.