Negative thermal expansion compounds and their mechanisms

A review is presented of recent progress in the field of negative thermal expansion (NTE), including compounds, mechanisms, and their possible applications.This is a new and promising research field that emerged in the last decade.So far, more and more compounds of many kinds have been found to exhibit NTE, including ZrW2O8-like compounds with an open framework, magnetic alloys, anti-perovskite Mn3AX,PbTiO3-based ferroelectric compounds,and nano-particles.The NTE mechanism with respect to atomic thermal vibration has been successfully applied to certain NTE compounds with an open framework.However, the mechanism for other NTE compounds is correlated to non-vibration effects,such as those caused by spontaneous magnetovolume effects,ferroelectric spontaneous polarization,electrons, and particle size.Finally, some suggestions are proposed for the improvement of future applications of NTE materials.