The Ba1−ySryMnO3−x system

Subsolidus phase relations at ambient atmospheric pressure and elevated temperatures in the Ba_1?ySr_yMnO_3?x system were investigated by quenching, gravimetric, and X-ray diffraction methods. The system is not binary above ～1035°C because of reactions with atmospheric oxygen. The air isolar, P_O2 = 0.2 atm, was characterized at 1225, 1375, 1490, and 1610°C. Seven oxygen-deficient phases including a perovskite phase characterize the system. Their stability depends on the values of y and x in Ba_1?ySr_yMnO_3?x. The cell dimensions of these phases expand as x increases at fixed y. These seven modifications can be retained in stoichiometric form by oxidation at lower temperatures.