Abstract
Recently developed lead-free incipient piezoceramics are promising candidates for off-resonance actuator applications due to their exceptionally large electromechanical strains. Their commercialization currently faces three critical challenges: the high driving electric field required for delivering the potentially large strains; large strain hysteresis, which is inappropriate for precision devices; and relatively high temperature dependencies. We propose that instead of utilizing incipient piezoelectric strains, harnessing the maximum possible electrostriction would provide a highly effective way to resolve all these challenges. This concept was experimentally demonstrated using textured 0.97Bi1/2(Na0.78K0.22)1/2TiO3-0.03BiAlO3 as an exemplary incipient piezoceramic, whereby texturing was achieved using a reactive templated grain-growth technique. The manufactured textured ceramic is characterized by Smax/Emax of 995 pm V−1 and an electrostrictive coefficient, Q33, of 0.049 m4 C−2. Both these parameters are as large as those of single crystals. The current work presents a significant advancement in the field of lead-free ceramics and can guide future efforts in this direction. In addition, the concept presented here can be easily transferred to other disciplines involving the design of functional properties of various materials.
Highlights
Since the first report on incipient piezoelectric strain (IPS) in a (Bi1/2Na1/2)TiO3 (BNT)-based lead-free ceramic,[1] there have been numerous attempts to enhance the strain properties of these materials. These studies have concluded that IPS is a common feature of relaxor ferroelectrics as long as their freezing temperature is below room temperature, that is, they are in the ergodic relaxor state, whereas ferroelectric long-range order is only stable under the application of a certain or higher electric field.[2,3,4]
Most useful IPSs have been found in relaxor ferroelectrics,[3,5] indicating that the inherently large poling field, Epol, with a large hysteresis, is unavoidable
The strain characteristics of samples prepared by conventional solid-state reaction (CSSR) methods have a series of challenges to overcome, including large hystereses, large driving electric fields and relatively large temperature dependence
Summary
Chang Won Ahn[1], Gangho Choi[1], Ill Won Kim[1], Jae-Shin Lee[2], Ke Wang[3], Younghun Hwang[4] and Wook Jo4. Developed lead-free incipient piezoceramics are promising candidates for off-resonance actuator applications due to their exceptionally large electromechanical strains. Their commercialization currently faces three critical challenges: the high driving electric field required for delivering the potentially large strains; large strain hysteresis, which is inappropriate for precision devices; and relatively high temperature dependencies. We propose that instead of utilizing incipient piezoelectric strains, harnessing the maximum possible electrostriction would provide a highly effective way to resolve all these challenges This concept was experimentally demonstrated using textured 0.97Bi1/2(Na0.78K0.22)1/2TiO3-0.03BiAlO3 as an exemplary incipient piezoceramic, whereby texturing was achieved using a reactive templated grain-growth technique. NPG Asia Materials (2017) 9, e346; doi:10.1038/am.2016.210; published online 27 January 2017
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