Rietveld texture analysis of complex oxides: examples of polyphased Bi2223 superconducting and Co349 thermoelectric textured ceramics characterization using neutron and X-ray diffraction

摘要

Orientation distributions of cobaltite thermoelectric and polyphased bismuth-based cuprate superconducting textured materials are determined from neutron and X-ray diffraction analysis. Curved position-sensitive detectors coupled to a tilt-angle (chi) scan enable the treatment of the whole diffraction pattern using the combined Rietveld - WIMV - Popa algorithm. The textures of three phases of superconducting compounds are determined. The critical current densities, measured for four samples, are strongly dependent on the calculated texture strengths, crystallite sizes and phase ratios. For the cobaltite compounds, a comparison between X-ray and neutron analysis shows the advantages of the latter technique for avoiding the limitations of the X-ray analysis with respect to the defocusing effect. The results highlight the necessity and efficiency of the combined approach for a quantitative texture analysis of complex materials and exemplify the texture - anisotropic physical properties relationship for a better understanding and design of improved bulk superconducting and thermoelectric materials.