Crystal Structure and Physicochemical Properties of Solid Solutions Ba0.5Sm0.5Fe1–yMnyO3–δ

Abstract

Based on the results of XRD analysis of samples with the general formula Ba_0.5Sm_0.5Fe_1–yMn_yO_3–δ, obtained using glycerol-nitrate technique with subsequent annealing at 1300°C in air, it was established that the homogeneity range of solid solutions with a cubic structure (space group \(Pm\bar {3}m\)) is in the interval 0.15 ≤ y ≤ 0.45. It is shown that the unit cell parameters of Ba_0.5Sm_0.5Fe_1–yMn_yO_3–δ decrease with increasing manganese content. The oxygen deficiency (δ) in air at room temperature at a low manganese content (y = 0.15), determined by the iodometric titration method, does not exceed 0.1, and the oxygen content in oxides with y = 0.25 and 0.45 is close to stoichiometric. The linear thermal expansion coefficients (LTEC) of Ba_0.5Sm_0.5Fe_1–yMn_yO_3–δ, obtained from dilatometric measurements, are in the range of (12.7–14.2) × 10^–6 K^–1 and are comparable with the LTEC of widely used electrolytes based on cerium oxide and zirconium oxide. It is shown that the relative thermal expansion of Ba_0.5Sm_0.5Fe_1–yMn_yO_3–δ decreases with increasing manganese content. The temperature dependences of the total electrical conductivity of Ba_0.5Sm_0.5Fe_1–yMn_yO_3–δ (y = 0.15, 0.35) have a maximum. The increase in electrical conductivity in the low-temperature region is explained by the increase in the mobility of charge carriers. The decrease in electrical conductivity in the high-temperature region is due to a decrease in the concentration of charge carriers (holes), which is associated with an increase in oxygen deficiency.