Synthesis, structure and oxygen nonstoichiometry of La0.4Sr0.6Co1-yFeyO3-δ

The samples of La0.4Sr0.6Co1-yFeyO3-delta (y=0.2 and 0.4) were prepared using both conventional ceramic technique and nitrate-citrate precursors technique. The phase identification was made by X-ray diffraction method. The refinement of structural parameters from the XRD and neutron diffraction measurements was performed by full profile Rietveld analysis. Neutron diffraction showed that both samples possess distorted perovskite-type structure. Oxygen nonstoichiometry was measured by chemical analysis and then mogravi metry TG) analysis in the range 20 <= T/degrees C <= 900 and 2E-5 <= pO(2)/atm <= 4E-1. TG-experiments indicate a relatively fast and reversible oxygen exchange at pO(2) > 1E-2 atm. Mass saturation occurs at T < 300 degrees C upon cooling. The absolute value of oxygen nonstoichiometry was determined by iodometric titration measurements. It was found that both samples have practically stoichiometric composition at 300 degrees C in air and 5 increases with increasing temperature and decreasing oxygen partial pressure. (C) 2007 Published by Elsevier Ltd.