USE OF CREEP TO INVESTIGATE MASS TRANSPORT IN (La,Sr)MnO_3

摘要

The creep behavior of fine-grained (La_(1-x)Sr_x)_(1-y)MnO_3 (LSM) with x≈0.1, 0.2 and 0.3 and y≈0.03 to 0.04 was investigated as a function of oxygen partial pressure (PO_2) at 1250℃. For (La_(1-x)Sr_x)_(1-y)MnO_3 with x≈0.1, 0.2 an oxygen partial pressure exponent, m≈0.25 was observed at low oxygen partial pressures. At high oxygen partial pressures, m≈-0.16. For (La_(0.7)Sr_(0.3))_(1-y)MnO_3 only, m≈0.25 was exhibited over the entire PO_2 range tested. The m values were not in agreement with the simple point defect model for LSM. The simple defect-chemistry model for LSM was modified based on cation non-stoichiometry. The modified defect-chemistry model yielded excellent agreement between the predicted and experimental m values. The effect of oxygen activity on deformation suggested that the rate-controlling defects are cation vacancies at low oxygen partial pressures and oxygen vacancies at high oxygen partial pressures.