BERKELEY, CA There is good news for the global effort to reduce the amount of lead in the environment and for the growing array of technologies that rely upon the piezoelectric effect. A lead-free alternative to the current crop of piezoelectric materials has been identified by researchers with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC), Berkeley.
The key to this success is the use of bismuth ferrite, a compound with a perovskite crystal structure, meaning it has crystal planes of oxygen and bismuth atoms alternating with planes of oxygen and iron atoms. These planes can move relative to one other when the proper strain is applied. The research team discovered that the piezoelectric effect in bismuth ferrite becomes significantly enhanced in response to the application of epitaxial strain -compression in the direction of its crystal planes.
"We have demonstrated that epitaxial strain can be used to create a large piezoelectric responses in thin films of bismuth ferrite," says Ramamoorthy Ramesh, a materials scientist who led this research. "The piezoelectric effect is reversible when the strain is relaxed."
Ramesh holds joint appointments with Berkeley Lab's Materials Sciences Division and UC Berkeley's Department of Materials Science and Engineering and the Department of Physics. He is the senior author on a paper published in the journal Science entitled: "A Strain-Driven Morphotropic Phase Boundary in BiFeO3."
Co-authoring the paper with Ramesh were Robert Zeche, Marta-Dacil Rossell, Jinxing Zhang, Alison Hatt, Qing He, Chan-Ho Yang, Amit Kumar, Chih-Hubng Wang, Alexander Melville, Carolina Adamo, Ying-Hao Chu, Jon Ihlefeld, Rolf Erni, Claude Ederer, Venkatraman Gopalan, Long-Qing Chen, Darrell Schlom, Nicola Spaldin and Lane Martin
"In principle, the strain-driven piezoelectric effect we have observed in bismuth ferrit
|Contact: Lynn Yarris|
DOE/Lawrence Berkeley National Laboratory