High-temperature deformation and defect chemistry of (La1-xSrx)1-yMnO3+δ

The creep behavior of (La1-xSrx)(1-y)MnO3+delta has been studied as a function of oxygen partial pressure (P-O2) and Sr concentration. Polycrystalline samples (x = 0.1, 0.2, 0.3) were deformed at 1523 K in constant-crosshead-speed compression tests in various atmospheres (10(-2) less than or equal to P-O2 less than or equal to 10(5) Pa). The material deformed by grain-boundary sliding accommodated by lattice diffusion with some possible cavitation and/or interface reaction control. The defect-chemistry model which is standard in the literature could not explain the dependence of the stress on P-O2 and the Sr concentration. A modified defect-chemistry model shows that cation vacancies controlled the creep rate at P-O2 less than or equal to 10(5) Pa for x = 0.3 and at low P-O2 for x = 0.1 and 0.2, and that oxygen vacancies were rate-controlling at high P-O2 for x = 0.1 and 0.2. (C) 1999 Acta Metallurgica me. Published by Elsevier Science Ltd. All rights reserved.