ADVANCED MATERIALS WITH NEGATIVE THERMAL EXPANSION

The isotropic negative thermal expansion compound,ZrW2O8,has been intensively studied since 1996.A variety of newly discovered materials which show even larger negative thermal expansion than that of ZrW2O8 are presently under consideration,namely CN-bridged compounds,ferroelectric ceramics,anti-perovskite manganese nitrides and nanoparticles.The mechanisms associated with the negative thermal expansion effect of these compounds are discussed in terms of their vibrational structures or in terms of their magnetic or electronic transitions.The materials with a large negative thermal expansion coefficient have potentially useful for preparing composites which are insensitive towards temperature changes.