Synthesis and photoluminescent characteristics of Sr2CeO4 phosphors prepared via a microwave-assisted solvothermal process

Blue-light emitting Sr₂CeO₄ phosphors were successfully prepared via a microwave-assisted solvothermal method employing ethylene glycol as a solvent. The formation of Sr₂CeO₄ phase began when the solvothermally derived precursors were heated at 800 °C. With increase in heating temperatures, significantly enhanced excitation and emission intensities were observed because of an increase in the amount of Sr₂CeO₄. Heating at 1200 °C led to a substantial decrease in mission intensity due to thermal decomposition of Sr₂CeO₄ at elevated temperatures. The solvothermally derived Sr₂CeO₄ was found to exhibit higher emission intensity than the solid-state-reaction-derived phosphors. According to the deconvoluted emission spectra, two emission peaks are attributed to two metal-to-ligand charge-transfer states. Based on the deconvoluted results, a qualitative energy-level diagram of Sr₂CeO₄ was proposed. VUV-excited luminescence studies for Sr₂CeO₄ indicate that one peak at 193 nm is assigned to the charge-transfer transition between Sr²⁺ and O²⁻.