Determination of the depth distribution of subsurface damage during polishing of alumina

High-resolution grazing-incidence parallel-beam powder diffraction has been used to detect the subsurface damage below alumina surfaces subjected to p olishing with cerium oxide or diamond. Despite very significant evolution o f the surface morphology, no changes in the subsurface strains were observe d over a 20 min period of polishing with ceria. For both polishing material s, the variation with angle in the full-width at half-height maximum was su ccessfully modelled by a strain distribution that fell exponentially with i ncreasing depth. Although the surface amplitude and depth dependence parame ter are coupled, we have been able to place upper limits on the depth to wh ich the damage extends. Under realistic assumptions, the depth of damage in duced by 1 mum diamond paste is comparable with that from 3 mum ceria polis h.