A new solid state synthesis methodology for ternary and higher order compounds

A persistent problem in the synthesis of complex materials from three or more constituents is the retention of very stable intermediate phases with properties grossly different from the target phase. In our recently developed two-stage synthesis methodology, a binary precursor is prepared and then directly converted into the product phase, thereby avoiding intermediate phase formation. Crystallographic similarities between the precursor and product phases are manipulated such that the major structural elements remain chemically intact. Ordered structural vacancies are used to facilitate rapid and highly selective diffusion of the third element into the precursor. Since no crystallographic reconstruction is required, no extraneous phases can form. The method has been tested on the solid state synthesis of Ti₃SiC₂ and Ti₃AlC₂, producing synthesis temperature reductions of 400 – 600°C. It is postulated that similar crystal structural relationships in layered oxides, nitrides and intermetallic compounds will allow an extension to many other systems.