Oxygen nonstoichiometry, defect structure and oxygen diffusion in the double perovskite GdBaCo2O6−δ

Abstract

Oxygen nonstoichiometry of GdBaCo₂O_6−δ was studied by means of the thermogravimetric technique in the temperature range 600–1000 °C. The defect structure model based on the simple cubic perovskite GdCoO_3−δ was shown to be valid for GdBaCo₂O_6−δ up to temperatures as low as 600 °C. Two independent methods, namely dc-polarization with the YSZ microelectrode and ¹⁸O-isotope exchange with gas phase analysis, were used to determine the oxygen self-diffusion coefficient in the double perovskite GdBaCo₂O_6−δ. All measurements were carried out using ceramic samples identically prepared from the same single phase powder of GdBaCo₂O_6−δ. The experimental data on oxygen nonstoichiometry of GdBaCo₂O_6−δ allowed a precise calculation of the oxygen interphase exchange rate and the oxygen tracer diffusion coefficient on the basis of the isotope exchange measurements. The values of the oxygen self-diffusion coefficient measured by the dc-polarization technique were found to be in very good agreement with the ones of the oxygen tracer diffusion coefficient.