Domain wall engineering in barium titanate single crystals for enhanced piezoelectric properties

For the [111] poled barium titanate (BaTiO3) single crystals with the engineered domain configuration, it was clearly observed that the piezoelectric properties increased with decreasing domain sizes. To explain the phenomenon, the multidomain single crystals were regarded as the composite of (a) a distorted domain wall region and (b) a normal tetragonal domain region. Using a 2-phases model, the piezoelectric properties from the domain wall were estimated. As a result, ultrahigh piezoelectric constants over 8,000 pC/N were expected from the domain wall region. Moreover this study suggested that it is possible to obtain the lead-free piezoelectric materials with the d(31) and d(33) over 1, 000 pC/N, when the domain sizes can decrease below 1 mu m.