SUCCESSFUL DESIGN OF NEW VERY LOW THERMAL EXPANSION CERAMICS.

In the last few years we have succeeded in developing three separate groups of near-zero-expansion ceramics. These are based on: (1) modification by crystalline solution of GeO//2 for SiO//2 in the well-known cordierite phase; (2) discovery of a new structural family known as left bracket NZP right bracket or left bracket CTP right bracket +0,many members of which have near-zero values of alpha and very extensive crystalline solution possibilities permitting continuous control of alpha ; (3) di- (or multi) phasic composites of phases, one with negative and one with positive alpha to give a net-zero- alpha ceramic material.