Rietveld texture analysis of alumina ceramics by neutron diffraction

The orientation distributions of alpha-Al2O3 textured ceramics are determined from neutron diffraction spectra. A curved position-sensitive detector coupled to a tilt angle (chi) scan allowed the whole diffraction pattern treatment in the combined Rietveld-WIMV-Popa algorithm. Four textured alumina ceramics were prepared by slip-casting under a high magnetic field and sintered at 800, 1300, 1400, and 1600 degreesC. The calculation of the distribution density, correlated to the representation of the normal and inverse pole figures, highlights the influence of the magnetic field and sintering temperature on the texture development. The principal pole figures show a pronounced (00l) texture: (001) pole parallel to the direction of slip-casting, and (110) pole with higher distribution density for the directions perpendicular to the expected fiber axis. The inverse pole figures calculated for the fiber direction show a major (001) component for all the samples. With the increasing sintering temperature, the texture strength is enhanced and the c-axis distribution is sharper. The effectiveness of the approach for determining the crystallite size is also evident. As a global trend, the calculated crystallite size and observed grain size are similar and increase with the increasing sintering temperature. The mechanism of the texture development in the sintered specimens is certainly initiated from the preferred orientation of the green body after slip-casting under a high magnetic field. The basal texture is enhanced during sintering by selective anisotropic grain growth. We evidenced here the powerfulness of the Rietveld texture analysis to provide a basis for the correlation of texture, microstructural parameters, and anisotropic properties.