New green energy material found

The material was developed by a research team led by Chu Ying-hao, an assistant professor in NCTU's Department of Materials Science and Engineering, along with other research groups in the United States and Ireland, NCTU President Wu Chung-yu said.

The study describing the discovery was published in the Nov. 13 edition of the prominent journal “Science.”

Piezoelectric materials can convert mechanical energy to electrical energy and vice versa.

Their most common application is in the battery-free quartz watch, where quartz crystals are piezoelectric, generating an electrical charge when mechanical pressure is applied to them and vibrating when an electrical charge is applied.

Chu pointed out that most traditionally high performing piezoelectric materials contain lead and often include two other materials to improve piezoelectric characteristics. Driven by a growing concern over the toxicity of lead-containing devices, however, the team found BiFeO3, which can be applied as a piezoelectric material and does not contain lead.

“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,” the research report said.

The morphotropic phase boundary is a transition region in a piezoelectric material in which the crystal structure changes abruptly and the electromechanical properties are at their maximum.

Chu noted that the new material's power generating performance is greater than for other lead-containing materials.

According to Chu, there are many ways to take advantage of the piezoelectric technology. For example, Israel plans to surface roads with piezoelectric materials to generate power through vehicle movement. The materials could also generate energy by coming into contact with tides, Chu said.

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