Crystal structure, ferroelectric and piezoelectric properties of epitaxial (1-x)(Bi0.5Na0.5)TiO3-x(Bi0.5K0.5)TiO3films grown by hydrothermal method

The composition dependencies of crystal structure, and electrical and electromechanical properties were systematically investigated for epitaxial films of (1-x)(Bi0.5Na0.5)TiO3-x(Bi0.5K0.5)TiO3[(1-x)BNT-xBKT (x = 0 -1)] deposited on (100)(c)SrRuO3//(100)SrTiO(3)substrates by a hydrothermal method. An In-plane crystal lattice was clamped by that of underlying SrRuO(3)irrespective of thexvalue. The dielectric constant decreased monotonously with increasingx. The polarization-electric field hysteresis loops were imprinted due to the preferential polarization in the films. In addition, the increase of tetragonality with increasingxvalue contributes to the increase of saturation and remnant polarization (P(sat.)andP(r), respectively), coercive field (E-c) as well asP(r)/P(sat.)values. The effective piezoelectric coefficient (nearE = 0 kV cm(-1)) improved considerably with increasingx, reaching a maximum of 62 pm V(-1)in the BKT film. A comprehensive and systematic study has been performed on (1-x)BNT-xBKT epitaxial films in this work, which lays the foundation for further research of this system in the future.