Characterization of superfine Sr₂CeO₄ powder prepared by microemulsion-heating method

Powder phosphor of Sr₂CeO₄ is prepared by microemulsion-heating method and a film of the phosphor on ITO glass is formed by electrophoretic deposition. Field emission scanning electron microscopy (FE-SEM) images show that the powder fired at 850°C for 4 h has a spherical shape with an average diameter of 70-80 nm whereas the powder sintered at 900°C for 4 h and 1000°C for 4 h have shuttle-like and spherical shapes, respectively, with both sizes less than 1 μm. X-ray diffraction (XRD) patterns indicate that the superfine Sr₂CeO₄ exhibits an orthorhombic crystal structure. Room-temperature photoluminescence (PL) measurements show that there are three excitation peaks located at around 262 nm, 280 nm and 341 nm, and all the Sr₂CeO₄ samples display an intense blue emission at 470 nm with CIE coordinate of (x, y)-(0.176, 0.283). The quantum yield of phosphor is high up to 0.47±0.04. Compared with Sr₂CeO₄ samples prepared with traditional high-temperature heating, the phosphor synthesized with this method has a smaller size, lower calcination temperature, and shorter calcination time, and the main excitation and emission bands are blue shifted about 30 nm and 12 nm respectively. The startup voltage for Sr₂CeO₄ film on ITO glass shifts from 2700 V to 4000 V with increasing thickness of the film.