Critical size and shape of CdO ex-Cd(OH)2 crystallites

The present paper reports the extent to which the size and shape of oxide crystallites resulting from a decomposition reaction depend on the crystallite size of the initial material. If those sizes are sufficiently large i.e. higher than “critical sizes”, the resulting oxide crystallites assume exactly these “critical sizes”. They are the maximum size that can be reached by oxide crystallites in the absence of any evolution process such as ageing or sintering and are specific to a particular shape of these crystals, which is independent of initial crystallite size. Alternatively, if the initial material crystals are below these “critical sizes”, at least in one direction, then the dimensions and shape of the oxide crystallites depend on the size of the initial crystallites. These results were interpreted within the framework of the structural conversion mechanism related to the decomposition reaction and showing great similarities with a shear transformation.