Evaluation of polishing damage in alumina

Grazing incidence X-ray scattering and line focus acoustic microscopy have been applied to the study of grinding, lapping and polishing processes on a lumina. Changes as a function of polishing time ill the near-surface densit y, measured from the critical angle for total external reflection of X-rays , were related to changes in the beating area and surface morphology. No re lation was found between the micrometre-scale roughness measured by a stylu s instrument and the integrated diffuse scatter, the latter being related t o the nanometre-scale roughness on the top of the polished mesas remaining after grain pull-out during the grinding and lapping process. The surface a coustic wave velocity was also found to vary with polishing time. These cha nges cannot be ascribed to changes in roughness and are believed to measure changes in the residual crack density.