Solid State Reaction Mechanism of SrO-CeO_2 System

The solid state reaction process of the mixture of SrCO3 and CeO2 powders with different Sr/Ce ratios was studied by using XRD and TG/DTA methods. The results show that only Sr2CeO4 phase is formed for a firing temperature lower than 950℃ while Sr2CeO4 and SrCeO3 phases are simultaneously developed in the initial stages of the reaction for a firing temperature above 950℃. In the initial stages of the reaction above 950℃, the major product is Sr2CeO4 for close to 950℃ and it becomes SrCeO3 above 1000℃. There are two types of formation mechanism for SrCeO3 and Sr2CeO4, respectively. When the firing temperature is above 1000℃, SrCeO3 is formed directly by SrO and CeO2 while Sr2CeO4 is created by SrCeO3 and SrO. However, SrO and CeO2 convert directly to Sr2CeO4 below 950℃ and SrCeO3 is produced by the reaction of Sr2CeO4 and CeO2 for close to 950℃. Based on these results, the reaction mechanism of SrO-CeO2 system is derived and the wrong results in the XRD data of SrCeO3 (JCPDS36-980) have been clarified. The fluorescence spectra of Sr2CeO4 show that the formation mechanism has effect on its excitation spectra.