| The phononic crystals(PC) consisting of periodic materials with diverse elastic modulus and mass density have great advantage in manipulating acoustic wave propagation and energy flow. By modulating the geometry and/or the constituent materials of the PC, many interesting phenomena can be realized, including band gap, negative refraction, and localized defect modes, which are promising for potential applications in cloaks, isolators, waveguides, sensors and filters. It is highly desirable to be able to tune the responses of PC on-demand during these applications, without the need to reconfigure the geometry or the constituents of PC, though large tunability is rather difficult to achieve in practice.Here, we report a tunable PC made of Ba0.7Sr0.3TiO3(BST) ceramics with the phase transition temperature TC at room temperature, across which the acoustical properties show substantial variation. PC consisting of periodic artificial structure on the surface of BST plate are found to be suitable for multi-frequency transmission enhancement, where transmission peaks show large thermal tunability around 20% over 20 K temperature range near room temperature. The phenomenon is attributed to the structured-induced resonant excitation of Lamb modes that exist intrinsically in the uniform elastic plate, while these Lamb modes are sensitive to the elastic properties(longitudinal and transverse wave velocities) of plate and can be modulated by temperature in BST plate around TC.Then we study the acoustic radiation force(ARF) tunibility based on BST PC, and find the ARF in 293 K is negative, while in 313 K is positive, whatmore, the negative force is more than 3 times of the positive one. The tunable PC via ferroelectric phase transition will pave a way to explore acoustic properties of ferroelectric materials and has promising prospects for tunable smart devices, such as temperature-tuned Lamb wave filter, sensor and acoustic manipulation. |
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