OXYGEN NONSTOICHIOMETRY IN PEROVSKITE-TYPE OXIDE, UNDOPED AND Sr-DOPED LaMnO_3

摘要

The oxygen nonstoichiometry of a perovskite-type oxide, undoped LaMnO_(3+d) and Sr-doped La_(1-x)Sr_xMnO_(3+d) (x = 0 - 0.5) was examined at temperatures between 600 and 1000℃ in oxygen pressure between 1 and 10~(-28) atm by thermogravimetry and coulometric titration. The oxygen content, 3+d, in the oxide series La_(1-x)Sr_xMnO_(3+d) is changed from hyperstoichiometric region (d > 0), to hypostoichiometric region (d < 0), through stoichiometric region (d = 0). The oxide of x = 0 and 0.1 are decomposed into the component oxides, La_2O_3, SrO and MnO. The oxides of x > 0.2 is decomposed through (La,Sr)_2MnO_4 to the component oxides. The partial molar enthalpy and entropy of La_(1-x)Sr_xMnO_(3+d) (x = 0 - 0.5) were calculated.