Rietveld refinement and estimation of residual stress in GDC-LSCF oxygen transport membrane ceramic composites

The phase purity and crystal structure of dual-phase Ce9Gd.1O2-delta-La.6Sr.4Co.2Fe.8O3-delta (GDC-LSCF) composites were refined using data obtained from X-ray diffraction (XRD) by employing the Rietveld method. Rietveld analysis indicated that the structures of GDC and LSCF phases are well crystallized as cubic Fm (3) over bar m and rhombohedral R (3) over bar c space groups, respectively. Scanning electron microscopy images showed smooth and dense structures, depicting a homogeneous crystalline structure of the samples. When the composites were cooled from their sintering temperature (1250 degrees C), compressive stresses were generated in the GDC and corresponding tensile stresses were generated in the LSCF due to differences in thermal expansion coefficients. The compressive residual stresses of the composites were investigated by high-angle XRD measurements using the well-known sin(2)psi method. The average compressive residual stresses in GDC phase are estimated to be - 312 and - 290 MPa for 80 GDC-20 LSCF and 50 GDC-50 LSCF, respectively. The aim of this study is to provide a better understanding of the crystal structures and residual stresses in GDC-LSCF composites through XRD and the suitability of these composites for oxygen transport membranes.