Preparation and characterization of Li_0.25Sr_0.5(MoO₄):Eu _0.253+ red-emitting phosphors for white LEDs by organic gel-thermal decomposition process

摘要

Li_0.25Sr_0.5(MoO₄):Eu_0.253+ red-emitting phosphors were prepared by the organic gel-thermal decomposition process with metal salts and citric acid as starting reagents. X-ray diffraction, scanning electron microscopy and photoluminescent spectroscopy were used to characterize the as-prepared phosphors. The Li_0.25Sr_0.5(MoO₄):Eu_0.253+ phase consisting of nanosized crystallites is formed at 400 °C and the nanosized crystallites with a tetragonal-dipyramid morphology increase with the calcination temperature and time. During the early period at 650 °C, the microstructure of the Li_0.25Sr_0.5(MoO₄):Eu_0.253+ crystallites are unstable and the re-crystallization for some particles takes place with a particle morphological modification. The optimized calcination conditions for the Li_0.25Sr_0.5(MoO₄):Eu_0.253+ phosphors are 650 °C for 13 h. The Li_0.25Sr_0.5(MoO₄):Eu_0.253+ phosphors with particle sizes about 0.5 to 2.0 μm obtained under the optimized conditions can be excited by the ultraviolet light 395 nm and blue light 466 nm, which are well met with the requirements for the current commercial near-UV and blue LEDs, and exhibit a high emission performance.