Synthesis and Luminescent Properties of Superfine Sr2CeO4 Phosphors by Sol-Gel Auto-Combustion Method

Citric acid complexing sol-gel auto-combustion method was explored to synthesize superfine Sr2CeO4 phosphors using the inorganic salts Sr(NO3)2 and Ce(NO3)3 as raw materials together with citric acid (CA) as a chelating agent. TG-DTA, XRD, SEM and photoluminescence spectra were used to investigate the formation process, microstructure and luminescent properties of the synthesized Sr2CeO4. The results show that the crystallization of Sr2CeO4 begins at about 800 °C and completes around 900 °C with an orthorhombic structure. When the calcination temperature is above 1000 °C, Sr2CeO4 partly decomposes into SrCeO3. SEM studies show that the particles of Sr2CeO4 obtained at 900 °C are spherical-like shape and superfine with diameter below 100 nm. The excitation spectrum of the superfine Sr2CeO4 phosphors displays a broad band with two peaks around 290 and 350 nm respectively. The former peak is stronger than the latter one. This broad band is due to the charge transfer (CT) band of the Ce4+ ion. Excited by a radiation of 290 nm, the superfine phosphors emit a strong blue-white fluorescence, and the emission spectrum shows a broad band with a peak around 470 nm, which can be assigned to the f→t1g transition of Ce4+. It is found that the emission intensity is affected by the calcination temperature.