Oxide CMCs: interphase synthesis and novel fibre development

Strategies which have been used in the synthesis of high temperature interphases with debond capability in oxide/oxide systems have been: (i) the formation of layered oxides (β-aluminas or magnetoplumbites) with preferred crystal orientation due to in-situ interface reactions between phases deposited from vapour or liquid precursors and (ii) the deposition on fibre surfaces of complex oxides (vanadates and phosphates, principally of the rare earths) from colloidal precursors or by magnetron sputtering. This paper is primarily concerned with the latter. The constitution and thermal stability of these interphases has been studied with reference to potential fibres and matrices (alumina, YAG and mullite). Included within the program are newly developed single phase mullite fibres and examples of these are also presented.