The impedance step between different materials inevitably leads to serious energy loss during acoustic emission, transmission, and receiving. In this paper, a tunable gradient impedance matching layer (TGIML) was designed and fabricated to eliminate the impedance step. The TGIML was composed of periodical piezoelectric disks with shunting capacitors. Through the elaborate modulation of the capacitances of the shunting capacitors, the proposed TGIML can adapt interfaces formed by different materials. Two interfaces formed by solid rods were constructed to demonstrate the performance of the TGIML. The simulated and experimental results verified that, after inserting the TGIML, the transmission could be enhanced significantly in a wide frequency range for both interfaces. We believe that the proposed TGIML has great potential for wide applications in the development of ultrasound transducers, nondestructive testing, and energy harvesting.

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