Preparation of {100}-oriented (1−x)(Bi,K)TiO3−xCaTiO3 solid-solution epitaxial films by the hydrothermal method and their ferroelectric and piezoelectric properties

Abstract (1− x )(Bi,K)TiO 3 − x CaTiO 3 epitaxial films with x = 0–1.0 were grown on (100) c SrRuO 3 //(100)SrTiO 3 substrates by the hydrothermal method. The film composition region can be divided into three in view of its crystal structure. The films in the range of x = 0–0.12 (Region 1) and 0.60–1.0 (Region 3) consisted of a single phase and their lattice parameters changed with the x value. This suggests the formation of a solid solution. On the other hand, two phases coexisted in the intermediate range of x = 0.18–0.43 (Region 2). The ferroelectricity and the effective transverse piezoelectric coefficient, effective d 33 , were observed for the films in Regions 1 and 2. The slope difference of P r and the effective d 33 against x can be explained by the change in the tetragonality of the films with x in Region 1 and the volume fraction of the ferroelectric phase in Region 2.