A new approach to the study of solid-state reactions

A new technique for the study of solid-state reactions is described. The new approach uses a thin-film specimen geometry and is ideal for transmission-electron-microscopy studies of the same specimen before and after the Occurrence of solid-state reactions. The technique of illustrated by an investigation of the growth of Ni-Al spinel on, and into, an alumina substrate. Near-topotactic relationships and exact topotactic alignment of the spinel and the alumina were both found. The {111} plane of the spinel is parallel either to the (00011) plane of the alumina or to the {11 2 0} plane of the alumina. Further heat treatment of such samples directly reveals the mechanism by which the spinel particles grow.