Depth-profiling of phase composition and preferred orientation in a graded alumina/mullite/aluminium-titanate hybrid using X-ray and synchrotron radiation diffraction

X-ray diffraction (XRD), grazing-incidence synchrotron radiation diffraction (GISRD) and multi-wavelength synchrotron radiation diffraction (MWSRD) have been successfully used for near-surface depth profiling of phase composition and texture in a functionally-graded alumina/mullite/aluminium-titanate hybrid prepared by an infiltration process. Depth profiling of near-surface information both in the nanometer and micrometer scale has been done by (a) varying the X-ray wavelength, (b) varying the grazing-incidence angle, and (c) gradual polishing of the sample surface with diamond lap. Results show a distinct gradation in the phase abundance near the surface of the hybrid sample. The distribution of mullite near the surface is highly textured and shows a distinct depth-dependent gradation in preferred grain-orientation. The unique but powerful capability of XRD, GISRD and MWSRD as complementary tools for depth profiling the near-surface region of graded materials has been demonstrated in this work.