Phase evolution in CeO2-doped SrTiO3

Phase evolution in the nominally cation stoichiometric compositions of CexSr1−xTiO3+x has been investigated when synthesized in air. Conventional solid state route is used to synthesize dense ceramic pellets of CexSr1−xTiO3+x (x = 0, 0.02, 0.04, 0.07, 0.10 and 0.15). SEM performed on the sintered pellets of doped compositions shows the presence of residual phase of CeO2 in the dark color matrix of perovskite phase. The lattice parameter of the perovskite phase of CexSr1−xTiO3+x decreases linearly on addition of CeO2. Further, an increasing amount of CeO2 residual phase is also observed in the perovskite phase matrix. A defect reaction mechanism is proposed which essentially describes the formation of perovskite with CexSr1−1.5xTiO3 stoichiometry in the nominally stoichiometric compositions, and explains the presence of residual CeO2 phase. Using the X-ray diffraction data, the molar ratio between the residual CeO2 and perovskite phases in the powder samples is calculated for various compositions, which supports the validity of the proposed defect reaction mechanism.