Stability of phases in (Ba, Gd)MnO3 solid solution system

The existing phases in BaxGd1-xMnO3 solid solution system (0 ≦ x ≦ 1) were studied by analyzing the detailed crystal structure of each composition from the results of the Rietveld method using powder X-ray diffraction data. For a small substitution of Ba for Gd (0 ≦ x < 0.1), the orthorhombic phase with a perovskite type structure (Pnma space group) was stably formed and this fact was supported by the electron diffraction data. There existed an intermediate phase of Ba0.33Gd0.67MnO3, which was characterized as the tetragonal phase with perovskite structure. The composition range of this phase was narrow and almost line compound. Between the regions of these phases, there existed two-phase region. There was also a two-phase region between the intermediate tetragonal phase and BaMnO3. Measurement of electrical conductivities of these orthorhombic solid solutions and tetragonal phases showed semiconducting behaviors for both phases and the existence of the phase transition at high temperature for the orthorhombic phase. The transition temperature decreased as the Ba content increased.