NZP: A New Family of Low Thermal Expansion Ceramics

The NZP family, which gets its name after the prototype composition NaZr2P3O12, has received much attention in recent times because of their very low coefficient of thermal expansion (CTE), controlled lattice thermal expansion anisotropy, fast ionic conductivity, high thermal and chemical stability and flexibility towards ionic substitutions. Such materials can find widespread applications as exhaust components in automobiles, mirror blank for optical telescope, substrate materials for electronic packaging, as well as in sulphur batteries, nuclear waste immobilization, port-liners for diesel engines, braze fixtures for aircraft engines etc. The low expansion behaviour of NZP materials has been attributed to: (i) strongly bonded 3—dimensional network structure, (ii) existence of structural holes which may absorb some of the thermal vibrations and (iii) anisotropy in the thermal expansion of the lattice. In this overview the crystal structure, synthesis, thermal expansion behaviour and possible applications of NZP materials have been described.