Publication Type:Journal Article
Source:Science, Volume 326, Number 5955, p.977-980 (2009)
Keywords:Article, bismuth, bismuth derivative, bismuth ferrite, chemical structure, electric field, electricity generation, Electrochemistry, electromagnetic field, energy, ferrite, global climate, molecular mechanics, morphotype, piezoelectricity, priority journal, surface property, unclassified drug
Piezoelectric materials, which convert mechanical to electrical energy and vice versa, are typically characterized by the intimate coexistence of two phases across a morphotropic phase boundary. Electrically switching one to the other yields large electromechanical coupling coefficients. Driven by global environmental concerns, there is currently a strong push to discover practical lead-free piezoelectrics for device engineering. Using a combination of epitaxial growth techniques in conjunction with theoretical approaches, we show the formation of a morphotropic phase boundary through epitaxial constraint in lead-free piezoelectric bismuth ferrite (BiFeO3) films. Electric field-dependent studies show that a tetragonal-like phase can be reversibly converted into a rhombohedral-like phase, accompanied by measurable displacements of the surface, making this new lead-free system of interest for probe-based data storage and actuator applications.
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