Analysis of grain boundaries by HREM

Abstract

The analysis of grain boundaries by HRTEM has shown that there are important differences between the structure of these defects in ceramic materials and similar defects in semiconductors and metals. These differences are illustrated by a new analysis of such defects in Mg-Al spinel. Spinel has a relatively large lattice parameter (0.809 nm) and can, therefore, be studied using a conventional 125 kV transmission electron microscope. It is shown that significantly greater detail will be accessible using the new generation of electron microscopes which have a point-to-point resolution of better than 0.2 nm. The defects discussed include coherent and incoherent twins and the {110} stacking faults. Experimental results at the lower resolution of 0.32 nm are compared with computer-simulated images for both the 125 kV and the new 400 kV transmission electron microscopes. The analysis of these defects in spinel is compared with both experimental and simulated images of closely related defects in germanium.