Low‐field piezoelectric coefficient and strain were investigated in Ca‐modified PbTiO₃ thin films by means of optical interferometry. A remanent piezoelectric coefficient of 70 pm/V was observed that agrees well with the values previously reported for the bulk ceramics of the same composition. The efficient poling of the films can be achieved at room temperature under the field of 300 kV/cm. Electrically induced strains as high as 0.8% were observed using a bipolar driving field of 1 MV/cm. Strain response under a unipolar driving field exhibited a good linearity and small hysteresis. These properties combined with the low dielectric constant and high dielectric strength are shown to be attractive for micromechanical applications.

We have investigated the occurrence of phase-change functional responses in the BiFeO₃-PbTiO₃ perovskite solid solution, analogous to those anticipated by a recent first-principles study of BiFeO₃-BiCoO₃. Like the former system, BiFeO₃-PbTiO₃ shows a morphotropic phase boundary (MPB) between multiferroic polymorphs of rhombohedral and tetragonal symmetries. MPB BiFeO₃-PbTiO₃ is a high temperature ferroelectric with the phase transition around 900 K, and a room temperature square-shape hysteresis loop with remnant polarization as high as 62 μC cm⁻². Strain under the electric field was studied, and a phase-change response was found. Analogous magnetoelectric effects are expected from the multiferroic nature of this MPB.

Phases, domain configuration, and properties of $0.65\mathrm{Pb}\left({\mathrm{Mg}}_{1∕3}{\mathrm{Nb}}_{2∕3}\right){\mathrm{O}}_3–0.35\mathrm{Pb}\mathrm{Ti}{\mathrm{O}}_3$ ceramics with grain sizes of 4 and $0.15\mu \mathrm{m}$ have been studied. The average phase is monoclinic Pm in coexistence with tetragonal. An evolution from micron-sized lamellar domains towards submicron/nanometer sized crosshatched domains is found with the decrease in size, which results in electrical relaxor type behavior and hindered switching. This is proposed to be associated with the slowing down of the relaxor to ferroelectric transition that causes the long time presence of an intermediate domain configuration. Nevertheless, a high sensitivity piezoelectric submicron-structured material is obtained under tailored poling $(d_{33}\sim 300\mathrm{pC}{\mathrm{N}}^{-1})$ .