Crystal Structure and Properties of Gd[sub.1-x]SrIx/ICo[sub.1-y]FeIy/IO[sub.3-δ] Oxides as Promising Materials for Catalytic and SOFC Application

A series of samples with the overall composition Gd[sub.1-x]SrxCo[sub.1-y]FeyO[sub.3-δ] (x = 0.8; 0.9 and 0.1 ≤ y ≤ 0.9), which are promising materials for catalytic and SOFC application, was prepared by a glycerol nitrate technique. X-ray diffraction analysis allowed to describe Gd[sub.0.2]Sr[sub.0.8]Co[sub.1-y]FeyO[sub.3-δ] with 0.1 ≤ y ≤ 0.5 in a tetragonal 2ap × 2ap × 4ap superstructure (SG I4/mmm), while oxides with 0.6 ≤ y ≤ 0.9 exhibit cubic disordered perovskite structure (SG Pm-3m). All Gd[sub.0.1]Sr[sub.0.9]Fe[sub.1-y]CoyO[sub.3-δ] oxides within the composition range 0.1 ≤ y ≤ 0.9 possess the cubic perovskite structure (SG Pm-3m). The structural parameters were refined using the Rietveld full-profile method. The changes of oxygen content in Gd[sub.1-x]SrxCo[sub.1-y]FeyO[sub.3-δ] versus temperature were determined by thermogravimetric analysis. The introduction of iron into the cobalt sublattice leads to a gradual increase in the unit cell parameters and unit cell volume, accompanied with increasing oxygen content. The temperature dependency of conductivity for Gd[sub.0.2]Sr[sub.0.8]Co[sub.0.3]Fe[sub.0.7]O[sub.3-δ] exhibits a maximum (284 S/cm) at ≈600 K in air. The positive value of the Seebeck coefficient indicates predominant p-type conductivity in the Gd[sub.0.2]Sr[sub.0.8]Co[sub.0.3]Fe[sub.0.7]O[sub.3-δ] complex oxide.