EFFECT OF MECHANICAL GRINDING ON THE HEXAGONAL STRUCTURE OF CDSE

The wurtzite-sphalerite dimorphism of CdSe is studied by following the effect of high-energy mechanical grinding on the wurtzite form. X-ray powder-diffraction patterns are collected at different grinding times . A. drastic modification in the initial wurtzite pattern is found alr eady after 90 min grinding. The main effect is the progressive quenchi ng of those Bragg reflections of wurtzite that are absent in the patte rn of the sphalerite. A sphaleritelike pattern, with broadened peaks, results after 72 h grinding. Energy dispersive x-ray diffraction and d ifferential scanning calorimetry both indicate the absence of any stru ctural modification induced by thermal heating only. Two different mod els are proposed to describe the effect of grinding. The first one is a two-phase model for a transition from wurtzite to sphalerite. The se cond one, based on the concept of latent parent structure, hypothesize s a transition towards an hexagonal disordered structure. The two mode ls are compared and discussed.