Thermal Stability and Anisotropic Thermal Expansion of SmBa_1−xSr_xCo₂O_5+δ (0.1 ≤ x ≤ 0.5)

Abstract

Bulk samples of SmBa_1−xSr_xCo₂O_5+δ were synthesized using solid-state chemical reaction of the starting metal oxides in the appropriate weight ratios and heating in air at temperatures approaching 1223 K. Their thermal expansion coefficients were determined using in situ x-ray diffraction studies between 298 K and 1273 K. No phase transition was observed during the heating or the cooling cycle. The volumetric thermal expansion coefficients for samples with orthorhombic Pmmm phase are 6 × 10⁻⁵ K⁻¹(x = 0.0), 6.8 × 10⁻⁵ K⁻¹ (x = 0.3) and 6.4 × 10⁻⁵ K⁻¹ (x = 0.5), and for sample with an orthorhombic phase Pnma 7.1 × 10⁻⁵ K⁻¹ (x = 1). The linear thermal expansion showed anisotropy of α_a or α_c > α_b for samples with Pmmm phase and no anisotropy for the x = 1 sample.