Thermoanalysis, nonstoichiometry and thermal expansion of La0.4Sr0.6Co0.2Fe0.8O3 − δ, La0.2Sr0.8Co0.2Fe0.8O3 − δ, La0.9Sr0.1Co1/3Fe1/3Ni1/3O3 − δ and La0.6Sr0.4Co0.2Fe0.6Ni0.2O3 − δ perovskites

In this work the results of thermogravimetric measurements and thermal expansion studies of La0.4Sr0.6Co0.2Fe0.8O3 − δ and La0.2Sr0.8Co0.2Fe0.8O3 − δ perovskites prepared by a “soft chemistry” EDTA based method are presented. The measurements performed on “as prepared” as well as on quenched samples allowed to calculate the relative change of the oxygen nonstoichiometry present at high temperatures. A high oxygen uptake during heating, proportional to the nonstoichiometry present in the sample, was recorded around 300–350 °C in case of the quenched samples. Also, thermogravimetric measurements were performed on La0.6Sr0.4Co0.2Fe0.6Ni0.2O3 − δ and La0.9Sr0.1Co1/3Fe1/3Ni1/3O3 − δ perovskites. Thermal expansion coefficient measurements of La0.4Sr0.6Co0.2Fe0.8O3 − δ and La0.2Sr0.8Co0.2Fe0.8O3 − δ oxides showed a linear characteristic of a relative elongation in the 50–500 °C range, however a much higher relative elongation was observed at higher temperatures. This phenomenon was related to the oxygen nonstoichiometry of the samples. Results of the transport properties measurements of La0.4Sr0.6Co0.2Fe0.8O3 − δ composition, performed at high temperatures as a function of the oxygen partial pressure, were also related to the oxygen nonstoichiometry δ.