Effect of MgO doping on the phase transformations of BaTiO₃

The successive phase transformations in MgO-doped BaTiO₃ were studied. Upon MgO doping, dielectric anomalies corresponding to lower phase transformations were broadened and depressed, while an anomaly for a cubic-tetragonal transformation remained and shifted to a lower temperature. XRD peak splitting upon tetragonality of BaTiO₃ was decreased, and the peaks exhibited abnormally broadened profiles which are different from the one for cubic BaTiO₃ above T_c. Raman spectroscopy revealed the existence of orthorhombic phase at room temperature for the solid solution with 0.5 mol% or more MgO. The temperature dependence of the Raman spectrum showed that orthorhombic and rhombohedral phases in MgO-doped BaTiO₃ were stabilized at higher temperatures than pure BaTiO₃.