Effect of vacuum sintering on the microstructure and spectroscopic properties of Eu doped strontium titanate ceramics

Abstract

In this work, we report on the optical properties of europium-doped SrTiO3, synthesized in situ via the sol-gel method as nanopowders and sintered ceramic bulks by heat treatment in vacuum. The structure and morphology of the Sr1-3x/2EuxTiO3 (x = 0.01–0.07) nanopowders and ceramics, concerning to the europium concentration, were characterized by X-ray powder diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The optical properties of as-prepared materials were also investigated. These analyses demonstrated that a temperature of 1425 °C in a vacuum of 10−4 Pa and a plateau of 4h are the optimal sintering conditions for Sr1-3x/2EuxTiO3 ceramics. Eu3+ doped SrTiO3 ceramics exhibit visible red photoluminescence characteristics. The emission of SrTiO3:Eu3+ phosphor with different amounts of Eu3+, excited by 395 nm and 465 nm light, was studied. The emission spectra exhibit characteristic luminescence from 5D0 → 7Fj (j = 0, 1, 2, 3, 4) intra-4f shell Eu3+ ion transitions. The most intense transitions are 5D0 → 7F1 (591 nm) for pumping at 395 nm and, 5D0 → 7F2 (615 nm) at 465 nm. The corresponding coordinates CIE for the Eu-doped SrTiO3 samples were calculated from the emission spectra obtained at 395 nm and 465 nm excitation wavelengths. This study demonstrates that the original protocol of materials engineering used is a simple and efficient method for manufacturing novel nanophosphors with enhanced reddish-orange emission. The as-obtained results indicated that the sol-gel synthesis combined with the sintering process in a vacuum at an appropriate temperature, plateau, could be a novel way to fabricate materials based on strontium titanate with reasonable optical properties.