[Formation mechanism of Sr2CeO4 and its effect on spectral properties]

The phase composition of SrCO3 and CeO2 (2:1) powder mixture calcined at different temperatures was identified by X-ray diffraction method. It was found that there were two types of formation mechanism of Sr2CeO4. When the starting powder mixture was fired above 1000 degrees C, the unstable intermediate phase SrCeO3 developed, which then reacted with SrCO3 to form the final product Sr2CeO4, however when the sintering temperature was lower, SrCO3 and CeO2 were converted directly to Sr2CeO4. The excitation spectra of Sr2CeO4 were quite different for different formation mechanism. The strong excitation band presented maxima at about 280 nm for the samples formed by the former mechanism, while the maxima were at about 254 nm for the samples formed by the latter mechanism. The formation mechanism had no effect on the emission spectra.