期刊
JOURNAL OF SOLID STATE ELECTROCHEMISTRY
卷 15, 期 5, 页码 1071-1075出版社
SPRINGER
DOI: 10.1007/s10008-010-1288-1
关键词
Calcium manganite; Perovskite; Oxygen non-stoichiometry; Phase diagram; Electrical properties; Charge disproportionation; Thermal expansion
资金
- Russian Foundation for Basic Research [10-03-00475a]
The oxygen content in CaMnO3-delta is studied by a coulometric titration technique depending on temperature and oxygen partial pressure variations in the ambient atmosphere. The delta-T phase diagram is derived from the obtained data where single-phase fields are outlined for orthorhombic, tetragonal, and cubic structures. The thermal expansion coefficient considerably larger in the cubic phase than in the tetragonal one is related with formation of large Mn3+ cations at depletion of oxygen from the crystalline lattice. Negative thermopower is explained by concomitant reactions of oxygen loss and charge disproportionation, 2Mn(4+) = Mn3+ + Mn5+. The forbidden energy gap in CaMnO3-delta is evaluated to be about 0.5 eV.
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