Application of a quantitative polyhedral analysis to the design of ceramic oxides

Abstract

The concept of cation coordination polyhedra can be developed into a quantitative framework for analysing the experimentally determined crystal structures of metal oxides. This framework considers both the connectivity of the polyhedra and the ratios of their volumes. An evaluation can thus be made of the possible structures which can be adopted by a given chemical composition. The approach can also be used to rationalise the geometrical constraints on cation sizes for any given structure to be stabilised. Three examples of its application are given. First, the stacking sequences observed in different ABO₃ compositions are rationalised. Secondly, an extension of the approach to an evaluation of void coordination polyhedra is outlined. Finally the structural and compositional dependence of ferroelectric properties is discussed, and a methodology for predicting new ferroelectric compositions defined.