High piezoelectricity by multiphase coexisting point: Barium titanate derivatives

BaTiO3-based lead-free piezoelectric materials have long been known as a mediocre class of piezoelectric materials. However, they have seen significant renewed interest in recent years ever since the discovery of high piezoelectricity in Ba(Zr, Ti)O-3-(Ba, Ca)TiO3 as well as the related Ba(Sn, Ti)O-3-(Ba, Ca)TiO3 and Ba(Hf, Ti)O-3-(Ba, Ca)TiO3 systems. The unexpectedly high piezoelectricity in this class of BaTiO3 (BT)-based materials is still not well understood and has stimulated significant research activity. We present a concise discussion of the notions leading to high piezoelectricity in BaTiO3-based systems. In particular, the possible role of a multiphase-coexisting point is highlighted.