Negative Thermal Expansion in Metastable PbVO ₃ : High‐Pressure Synthesis, Advances, and Perspectives

ABSTRACT Most materials expand on heating; however, some materials show the opposite trend, in which the overall volume contracts upon heating, a phenomenon known as negative thermal expansion (NTE). Materials exhibiting NTE are highly valued for their unique ability to tailor thermal expansion, especially in achieving zero thermal expansion when combined with positive thermal expansion materials. NTE functional materials illustrate the significant interplay between specific physical properties and NTE. In perovskite ferroelectric NTE materials, thermal expansion can be regulated through the interaction between ferroelectricity and NTE. The temperature‐induced ferroelectric‐to‐paraelectric phase transition is also accompanied by unusual NTE. Inspired by these, new NTE materials can be designed and realized in polar perovskites by stabilizing their metastable structures. Indeed, NTE was successfully realized in PbTiO 3 ‐type perovskite of PbVO 3 , which shows the same tetragonal perovskite structure as PbTiO 3 , but exhibits more pronounced tetragonal distortion. Recent progress of NTE in PbVO 3 ‐based derivatives has been summarized. NTE was achieved in PbVO 3 ‐based derivatives through chemical substitutions at the A‐site, B‐site, or anion site using a distinct high‐pressure synthesis method. Despite challenges in optimizing the performance of NTE, PbVO 3 ‐based perovskites provide a roadmap for discovering analogous materials such as BiCoO 3 , Bi(Zn 1/2 Ti 1/2 )O 3 , and Bi(Zn 1/2 V 1/1 )O 3 .