Compositional tuning and site selective excitations in SrTiO3:Y3+, Eu3+ red phosphors

Abstract The paper reports the effective control of charge transfer transitions in perovskite based titanate red emitting phosphors by site selective substitution and the resulting enhanced emission with increased colour purity. The influence of altering the substitution sites of Y3+ and Eu3+ ions at different cationic sites on local structure variations and photoluminescence properties is investigated by adopting three different protocols of composition, viz., Sr1-x-yYxTiO3: yEu3+, Sr1-x/2-yYxTi1-x/2O3: yEu3+ and Sr1-x/2-y/2YxTi1-x/2-y/2O3: yEu3+. It is found that optimum substitution of Y3+ ions at Sr2+ and Ti4+ sites in Sr0.95Eu0.05TiO3 enhances the intensity of luminescence by 14 times, accompanied by an increase in asymmetric ratio between 5D0→7F2 and 5D0→7F1 transitions from 1 to 5.6. Further, the double site substitution of Eu3+ and Y3+ ions in this system yields emission having close resemblance with that of the commercial red phosphor, Y2O3:Eu3+ with 99.9% colour purity, asymmetric ratio 6.8 and chromaticity co-ordinates (0.66, 0.34), close to that of standard red. The biexponential luminescence decay curves propose the occurrence of two nonequivalent Eu3+ crystallographic sites in Sr1-x-yYxTiO3: yEu3+ phosphors and the triple exponential behavior observed in the case of Sr1-x/2-yYxTi1-x/2O3: yEu3+ and Sr1-x/2-y/2YxTi1-x/2-y/2O3: yEu3+ shows the occurrence of three nonequivalent Eu3+ crystallographic sites. The increase in local asymmetry for Sr1-x/2-y/2YxTi1-x/2-y/2O3: yEu3+, which prompted the colour pure emission, compared to that of Sr1-x/2-yYxTi1-x/2O3: yEu3+, is evident in the increase of J-O intensity parameter (Ω2) from 6.07 × 10−20 to 8.98 × 10−20 cm2.