Present and future of piezoelectric single crystals and the importance of B-site cations for high piezoelectric response

High quality piezoelectric single crystals, such as Pb(Zn/sub 1/3/Nb/sub 2/3/)O/sub 3/-PbTiO/sub 3/ (PZNT) and Pb(Mg/sub 1/3/Nb/sub 2/3/)O/sub 3/-PbTiO/sub 3/ (PMNT), have been investigated, and, because their piezoelectric properties are greatly superior to those of Pb(Zr/sub 1-x/Ti/sub x/)O/sub 3/ (PZT) ceramics, they have been used for certain transducer applications since the late 1990s. The present situation for these relaxor-PT (lead titanate) single crystals is summarized. In this review, some possible high Tc > 200/spl deg/C single crystals are also introduced. Single crystals of Pb(In/sub 1/2/Nb/sub 1/2/)O/sub 3/-PbTiO/sub 3/ (PINT) binary system and Pb(Mg/sub 1/3/Nb/sub 2/3/)O/sub 3/-Pb(Sc/sub 1/2/Nb/sub 1/2/)O/sub 3/-PbTiO/sub 3/ (PSMNT) tertiary system have been synthesized, and their electrical properties are reported. In addition, a novel guiding principle for discovering excellent piezoelectric materials, namely the presence of low molecular mass B-site ions that can enter the lead-perovskite Pb(B'B")O/sub 3/ structure, is introduced.