The lead-free piezoelectric ceramics 0.82(Bi 0:5 Na 0:5 )TiO 3 -0.15BaTiO 3 -0.03(Bi 0:5 Na 0:5 )(Mn 1=3 Nb 2=3 )O 3 (abbreviated as BNT-BT-BNMN) was prepared by a conventional process of ceramic engineering. The X-ray diffractometer (XRD) analysis showed that all compositions could form a single perovskite phase. The ceramics showed excellent piezoelectric properties with a coupling factor k t ¼ 41%, a mechanical quality factor Q m ¼ 500, a piezoelectric constant d 33 ¼ 110 pC/N, a relative permittivity " T 33 =" 0 ¼ 520, a dissipation factor tan ¼ 0:66%, a Curie point T c ¼ 260 C, and a density ¼ 5:5 g/cm 3 . The physical properties of the ceramics were superior to those of hard Pb(Zr,Ti)O 3 (PZT). The high-power characteristics of the ceramics were superior to those of hard PZT. A cylinder sample of lead-free ceramics was used to fabricate a bolt-clamped Langevin transducer (BLT) for application in the ultrasonic cleaner. The vibration velocity of BLT using the ceramics was higher than that of hard PZT under the same input power. The cleaning effect of an ultrasonic cleaner using the BLTs was very high and sufficiently good for commercial application.

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Piezoelectric transducers are commonly operated at their resonance frequency. However, from a power dissipation standpoint, this is not the ideal driving frequency. In this paper, an optimized driving frequency in between the resonance and antiresonance frequencies is proposed for the piezo-transducer. First, the optimum driving frequency is characterized using a constant vibration velocity measurement method. The actual input power reveals the lowest power dissipation frequency between the resonance and the antiresonance frequencies, where the transducer behaves inductive. The electrical parameters of the transducer are then determined by an equivalent circuit formulation, which is useful for the electrical circuit analysis of the driver design. A Class E resonant inverter is used to design a capacitive output impedance driver at the optimized frequency by utilizing a series capacitor. Compared with the traditional resonance drive, driving at the optimized frequency reduces the required power by approximately half according to the measurements performed.