Crystal Structure and Properties of Gd1-xSrxCo1-yFeyO3-delta Oxides as Promising Materials for Catalytic and SOFC Application

A series of samples with the overall composition Gd1-xSrxCo1-yFeyO3-delta (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 Gd0.2Sr0.8Co1-yFeyO3-delta with 0.1 <= y <= 0.5 in a tetragonal 2a(p) x 2a(p) x 4a(p) superstructure (SG I4/mmm), while oxides with 0.6 <= y <= 0.9 exhibit cubic disordered perovskite structure (SG Pm-3m). All Gd0.1Sr0.9Fe1-yCoyO3-delta 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 Gd1-xSrxCo1-yFeyO3-delta 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 Gd0.2Sr0.8Co0.3Fe0.7O3-delta exhibits a maximum (284 S/cm) at approximate to 600 K in air. The positive value of the Seebeck coefficient indicates predominant p-type conductivity in the Gd0.2Sr0.8Co0.3Fe0.7O3-delta complex oxide.