Crystal structure, oxygen nonstoichiometry, thermal expansion and conductivity of (Nd,Sr)(Fe,Co)O3 − δ oxides

• The series of samples Nd1 − xSrxFe1 − yCoyO3 − δ were prepared by a glycerol nitrate technique.
• The phase composition and crystal structure of the samples were studied by powder X-ray diffraction.
• The changes of oxygen nonstoichiometry were determined using thermogravimetric analysis.
• Thermal expansion of ceramic samples versus temperature was measured.
• Total conductivity was measured by the four-probe DC technique.

A series of samples with overall composition Nd1 − xSrxFe1 − yCoyO3 − δ (x = 0.7, 0.0 ≤ y ≤ 1.0) and (y = 0.3, 0.0 ≤ x ≤ 1.0) were prepared by glycerol nitrate technique and characterized by X-ray diffraction, thermogravimetric analysis, iodometric titration and dilatometry. Nd1 − xSrxFe0.7Co0.3O3 − δ with 0.0 ≤ x ≤ 0.5 possesses orthorhombic structure (sp. gr. Pbnm) and reveals O-type → O/-type → O-type structural transition around x = 0.3. The orthorhombic distortion decreases with the increasing strontium substitution and solid solutions Nd1 − xSrxFe0.7Co0.3O3 − δ with 0.7 ≤ x ≤ 1.0 and Nd0.3Sr0.7Fe1 − yCoyO3 − δ with 0.0 ≤ y ≤ 1.0 exhibit the cubic structure (sp. gr. Pm3m). The structural parameters were refined using Rietveld full-profile analysis. The changes of oxygen content in Nd1 − xSrxFe1 − yCoyO3 − δ versus temperature were determined by the thermogravimetric analysis. The gradual substitution of neodymium by strontium or of iron by cobalt leads to the decrease of oxygen content. The thermal expansion measurements of Nd1 − xSrxFe0.7Co0.3O3 − δ (x = 0.3; 0.4; 0.5 and 0.7) were performed and chemical expansion constituents have been separated. The electrical conductivity significantly increased with strontium content in low temperature range. The influence of Sr content diminished in high temperature range.