Oxygen exchange in Pr1+xBa2-xCu3O6+z substitutional solid solutions

Pr1+xBa2-xCu3O6+z substitutional solid solutions prepared by solid-state reactions in air, using the appropriate metal nitrates as starting reagents, were studied by x-ray diffraction, microstructural analysis, and thermogravimetry (TG). The oxygen content of the synthesized materials was determined by iodometric titration. The TG data obtained at different heating rates were used to evaluate the apparent activation energy E-a for oxygen exchange between the solid and gas phases. The results indicate that the E-a for Pr1.4Ba1.6Cu3O6+z is much higher than those for the materials with x = 0, 0.25, and 0.6. The anomaly in E-a correlates with the variations in some other physicochemical properties of the solid solutions.