Domain Wall Engineering in Lead-free Piezoelectric Materials

抄録

Lead-free ferroelectrics have become highly attractive materials from the viewpoint of a solution to environmental problems. However, as compared with Pb(Zr,Ti)O3 (PZT) ceramics, their ferroelectric related properties were poor, and it is difficult to replace the PZT ceramics. To achieve much higher piezoelectric properties than those of PZT ceramics, the domain average engineering i.e., engineered domain configuration, is an important technique, and should be applied to lead-free ferroelectric materials. Barium titanate (BaTiO3) crystal is typical lead-free ferroelectrics and there have been a number of reports on its domain average engineering. Recently, for the tetragonal BaTiO3 crystals with the engineered domain configurations, it was found that the piezoelectric properties were significantly improved with increasing domain wall densities. This result suggests a possibility that the domain walls in the engineered domain configuration could contribute to the piezoelectric properties. Thus, to explain the domain wall contribution to the piezoelectric properties, the piezoelectric properties of the BaTiO3 crystals were investigated as a function of domain size. Moreover, this concept was applied to grain oriented BaTiO3 ceramics, and finally the lead-free piezoelectrics with d33 of 800 pC/N were prepared by domain wall engineering.