Ultrahigh electromechanical response from competing ferroic orders.

Materials with electromechanical coupling are essential for transducers and acoustic devices as reversible converters between mechanical and electrical energy. High electromechanical responses are typically found in materials with strong structural instabilities, conventionally achieved by two strategies-morphotropic phase boundaries and nanoscale structural heterogeneity. Here we demonstrate a different strategy to accomplish ultrahigh electromechanical response by inducing extreme structural instability from competing antiferroelectric and ferroelectric orders.

Origin of giant electric-field-induced strain in faulted alkali niobate films.

A large electromechanical response in ferroelectrics is highly desirable for developing high-performance sensors and actuators. Enhanced electromechanical coupling in ferroelectrics is usually obtained at morphotropic phase boundaries requiring stoichiometric control of complex compositions. Recently it was shown that giant piezoelectricity can be obtained in films with nanopillar structures.

Giant piezoelectricity in oxide thin films with nanopillar structure.

High-performance piezoelectric materials are critical components for electromechanical sensors and actuators. For more than 60 years, the main strategy for obtaining large piezoelectric response has been to construct multiphase boundaries, where nanoscale domains with local structural and polar heterogeneity are formed, by tuning complex chemical compositions. We used a different strategy to emulate such local heterogeneity by forming nanopillar regions in perovskite oxide thin films.

The role of Bi vacancies in the electrical conduction of BiFeO₃: a first-principles approach.

We employ first-principles methods to study the mechanism controlling the electrical conduction in BiFeO3 (BFO). We find that under oxygen-rich conditions, Bi vacancies (V(Bi)) have lower defect formation energy than O vacancies (V(O)) (-0.43 eV vs.