Relationship between mechanical grinding and photoluminescence of zirconia-toughened-alumina ceramics

Zirconia-toughened-alumina (ZTA) ceramics have been investigated by means of photoluminescence (PL) experiments at room temperature. Alumina and zirconia components of ZTA ceramics display characteristic PL emission spectra in the visible region. The spectrum for the former is confirmed to be originated in Cr3+ ion impurities while for the latter it does in FA-type centres (oxygen vacancy associated with an impurity). Samples mechanically polished and grown for one face with sandpaper — of different grades — show significant changes in the main PL spectral features with respect to untreated faces, also in time decay curves. The changes are discussed in terms of effects of microstructural variations by the mechanical grinding on the electron-hole recombination processes in the centres mentioned above. The main structural variation in the samples is related to the transformation of the tetragonal to the monoclinic phase of zirconia.