Perspective on the Development of Lead-free Piezoceramics

Authors


  • D. J. Green—contributing editor

  • This work was supported by the Deutsche Forschungsgemeinschaft under SFB 595 (Electric fatigue of functional materials) and by the state center ADRIA on adaptronics.

†Author to whom correspondence should be addressed. e-mail: roedel@ceramics.tu-darmstadt.de

Abstract

A large body of work has been reported in the last 5 years on the development of lead-free piezoceramics in the quest to replace lead–zirconate–titanate (PZT) as the main material for electromechanical devices such as actuators, sensors, and transducers. In specific but narrow application ranges the new materials appear adequate, but are not yet suited to replace PZT on a broader basis. In this paper, general guidelines for the development of lead-free piezoelectric ceramics are presented. Suitable chemical elements are selected first on the basis of cost and toxicity as well as ionic polarizability. Different crystal structures with these elements are then considered based on simple concepts, and a variety of phase diagrams are described with attractive morphotropic phase boundaries, yielding good piezoelectric properties. Finally, lessons from density functional theory are reviewed and used to adjust our understanding based on the simpler concepts. Equipped with these guidelines ranging from atom to phase diagram, the current development stage in lead-free piezoceramics is then critically assessed.

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