HRTEM and LACBED analysis of strain fields induced by the precipitation of chromium in alumina during internal reduction

During the internal reduction of the mixed oxide (Al, Cr)(2)O-3 the precipitation of metallic bcc chromium within the rhombohedral matrix of alumina follows only two types of orientation relationships which are associated to low energy configurations. Large stresses are expected to be produced by the volume decrease occuring during the reduction of Cr2O3 to metallic chromium and by the large misfit between the two structures. High resolution transmission electron microscopy (HRTEM) and large angle convergent beam electron diffraction (LACBED) techniques are applied to analyse the strain fields near the interfaces between the precipitates and the matrix.