Formation reaction and thermodynamic properties of SrCe sub(1-y)Eu sub(y)O sub(3-x)

TG-DTA and high-temperature X-ray diffraction measurements were carried out at temperatures from room temperature to 1623 K under various CO sub(2) partial pressures to study the formation of SrCe sub(1-y)Eu sub(y)O sub(3-x) from SrCO sub(3), CeO sub(2) and Eu sub(2)O sub(3) and also the reaction of the perovskite, SrCe sub(1-y)Eu sub(y)O sub(3-x), with CO sub(2) gas. For the formation reaction of SrCe sub(1-y)Eu sub(y)O sub(3-x) sample, two endothermic reactions are observed at 1198 and 1309 K in DTA curves. The former reaction corresponds to the crystal structural change of the carbonate from orthorhombic to hexagonal phase, whereas the latter one is the endothermic formation reaction of the perovskite together with the decomposition of SrCO sub(3). From the reaction of the perovskite with CO sub(2) gas, it is found that the Eu-doped SrCeO sub(3) sample is less stable than the undoped sample at constant temperature, because of smaller tolerance factor of the former.