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An Oxide with Shape Memory

In information storage field, multiferroic materials such as BiFeO3 and BFO draw a lot of researchers’ attention due to their unique properties. On recent Nature Communication, Jingxin Zhang and his colleagues from Department of Physics at Beijing Normal University reported their a new finding of a novel property on nano-BiFeO3—shape memory function.

At nano-scale, BiFeO3 shrinks upon cooling and it can recover to its original shape by applying electric field or heating stimuli. Comparing with traditional shape memory materials, BiFeO3 has much wider and more promising application in electronics such as integrated circuit. Jinxing Zhang noted:” This material can produce huge shape strain and might be used for driving and sensing infuture micro- or nano-motor systems.” These new findings may provide new insights and directions for researchers to explore potential applications for oxides.

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Upon electric field, pressure and heat stimuli, nano- BiFeO3 can form a whole shape memory loop. The material can reversibly transform between Martensitic-like structure and Austenitic-like structure within a strain range. *Image source: Jinxing Zhang et al.2013Nature Communications.

So far, most shape memory materials are metal-based materials and highest strain achieved is 8%. However, their practical application is difficult to implement because nano-scale metal (size<100 nm) usually show surface oxidation, surface tension effect, size effect and other possible undesired properties. “However, BiFeO3 accomplished 14% reversible strain and the oxide is stable structurally, and hence we can realize unique functionalities at nano-scale.” Jingxing Zhang said:” In addition, BiFeO3’s large strain can be used in electric field control and by using this material, the response frequency and driving force are significantly improved.” Moreover, current metal-based materials can’t integrate with semiconductor industry, while BiFeO3 is able to address this issue.

To take advantage of this material soon, researchers have to perform nano-structure design on BiFeO3 and construct nano-devices for different applications.  Researchers need more study on the material’s fatigue, fracture and other mechanical behaviors. “Understanding these questions is a necessary path to realize its application.” said Jinxing Zhang.

Source:Nature Communications