Synthesis, crystal structure and properties of SmBaCo2-xFe xO5+δ

Abstract

The solid solution formation range in the SmBaCo2-xFe xO5+δ (0≤x≤2) system examined at 1100 °C in air corresponds to 0≤x≤1.1. The crystal structure of SmBaCo 2-xFexO5+δ with x≤0.5 was described as orthorhombic (space group Pmmm), and with 0.6≤x≤1.1-as tetragonal (P4/mmm). The introduction of iron into the cobalt sublattice leads to a gradual increase of the unit cell parameters and volume, accompanied with increasing oxygen content determined by thermogravimetry. The dilatometric curves collected at 25-1100 °C in air exhibit moderate nonlinearities associated with the orthorhombic → tetragonal phase transition, as confirmed by the high-temperature X-ray diffraction analysis. Temperature dependencies of the electrical conductivity measured by 4-probe dc method in the temperature range 25-1000 °C in air display maxima at 300-350 °C, whilst the conductivity decreases with iron additions. These trends were discussed in terms of the defect structure and nature of the main charge carriers in SmBaCo 2-xFexO5+5. It was also shown that SmBaCo 2-xFexO5+δ is chemically stable with respect to the Ce0.8Sm0.2O1.9 solid electrolyte up to 1100 °C, but reacts with Zr0.85Y0.15O 1.93 even at 900 °C. © 2013 Elsevier Inc.