Thermogravimetric Analysis and Defect Models of the Oxygen Nonstoichiometry in La2–xSrxCuO4–y

The oxygen nonstoichiometry, y, of La_{2– x} Sr _x CuO_{4– y} (0 ≤ x ≤ 1) was determined as a function of temperature (800–1050°C) and oxygen partial pressure (10^–4 to 1 atm) by a thermogravimetric technique. The results were interpreted in terms of a number of defect models. It was found that a model based on the defect reaction 4Cu^×_Cu+ 2 V ^¨_o+ O_2(g)= 4Cu^._Cu+ 2O^×_o described the results well when the x and y dependences of the partial molar enthalpy of oxygen in the solid were considered. The large defect concentrations observed in this system lead to defect interactions, possibly ordering on the oxygen sublattice.