Phase transition behavior of mother phase of proton-conducting oxides, Sr 1− xBa xZrO 3

Abstract

The phase diagram of Sr 1− x Ba x ZrO 3, which is the mother phase of highly proton-conducting oxides, has been established by differential scanning calorimetry (DSC), dilatometry and X-ray diffraction analysis at various temperatures. The phase boundaries and order of the transitions from the primitive orthorhombic phase to the body-centered orthorhombic, tetragonal and cubic phases have been determined. The temperatures of these three kinds of phase transition decreased with increasing Ba content. The jump in the specific heat of the second-order phase transitions from primitive orthorhombic to body-centered orthorhombic and from tetragonal to cubic also decreased with increasing Ba content. An increase in Ba content decreased the variation in the enthalpy of the first-order phase transition from body-centered orthorhombic to tetragonal. The temperature region where high symmetry phases, such as the cubic and tetragonal phases, were stable expanded with increasing Ba content, which was in agreement with the tolerance factor approaching unity.