Enhanced Eu3+ red luminescence in scheelite based oxides, CaLaSbWO8

Abstract

Scheelite type tungstate based red phosphors, CaLa1-xSbWO8:xEu(3+) (x = 0.05, 0.10, 0.15, 0.20 0.25, 0.50 and 1) were synthesized by the conventional solid state method. The crystalline structure, morphology and photoluminescence of these phosphors were characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM) and spectrofluorimeter respectively. Investigations on photoluminescence properties show that these phosphors exhibit intense Eu3+ red luminescence (613 nm) under both near UV (394 nm), and blue (465 nm) excitations which corresponds to the D-5(0)-F-7(2) forced electric dipole transition of Eu3+. The analysis of XRD patterns and luminescence data points out that the distribution of Eu3+ is in highly ordered state with some aperiodicity which attributes for intense luminescence. On comparison, the emission intensity of CaLa0.5SbWO8:0.5Eu(3+) is one and half times stronger than that of commercial red phosphor, Y2O3:Eu3+. These phosphors are characterized by sharp red emission with shorter lifetimes and strong absorption strength at near UV (394 nm). The CIE color coordinates of the developed phosphors are (0.65, 0.34) that are comparable to the NTSC standard red phosphors.