THERMOGRAVIMETRIC ANALYSIS AND DEFECT MODELS OF THE OXYGEN NONSTOICHIOMETRY IN LA2-XSRXCUO4-Y

The oxygen nonstoichiometry, y, of La2-xSrxCuO4-y (0 less-than-or-equa l-to x less-than-or-equal-to 1) was determined as a function of temper ature (800-1050-degrees-C) and oxygen partial pressure (10(-4) to 1 at m) by a thermogravimetric technique. The results were interpreted in t erms of a number of defect models. It was found that a model based on the defect reaction 4Cu(Cu)x + 2V(o).. + O2(g) = 4Cu(Cu). + 2O(o)x des cribed the results well when the x and y dependences of the partial mo lar enthalpy of oxygen in the solid were considered. The large defect concentrations observed in this system lead to defect interactions, po ssibly ordering on the oxygen sublattice.