LFN and LSCFN perovskites — structure and transport properties

Structural, electronic and transport properties of LFN (LaFe1−zNizO3) and LSCFN (La1−xSrxCo1−y −zFeyNizO3) perovskites synthesized by a modified citric acid method were studied. Structure of the samples was characterized by X-ray studies with Rietveld method analysis. Magnetic properties and valence states of iron ions were characterized by 57Fe Moessbauer spectroscopy performed at RT, which were found to be greatly dependent on the chemical composition of the samples. Electrical conductivity was measured in the 20–800 °C temperature range and for some compositions relatively high values (exceeding 100 S cm− 1) were observed in the 600–800 °C range. Chemical stability studies in relation to Ce0.8Gd0.2O1.9 electrolyte, performed for selected perovskite samples, revealed decreasing stability with increasing Ni concentration and formation of solid solutions in CGO/perovskite composites. The coefficient of thermal expansion (CTE) of LFN perovskites was found to match that of CGO electrolyte (CTE in the 10–13 · 10− 6 K− 1 range).