Magnetoelectric (ME) coupling equivalent circuits for L-T (longitudinal magnetization and transverse polarization), L-L (longitudinal magnetization and longitudinal polarization), and C-C (circumferential magnetization and circumferential polarization) modes have been developed for laminated ME composites in prior reports. Here, we report the modeling of laminated magnetostrictive/piezoelectric bilayer composites operated in bending mode. By introducing the concept of mechanical voltage and mechanical current, a bending-mode ME coupling equivalent circuit was developed, which is useful to predict the ME coefficients in the region around the resonance frequency.

A small three-degree-of-freedom ultrasonic motor has been developed using a simple piezoelectric lead zirconate titanate (PZT)-tube stator (OD 5 mm, ID 3 mm, length 15 mm). The stator drives a ball-rotor into rotational motion around one of three orthogonal (x-, y-, and z-) axes by combing the first longitudinal and second bending vibration modes. A motor prototype was fabricated and characterized; its performance was superior to those of previous motors made with a PZT ceramic/metal composite stator of comparable size. The method for further improving the performance was discussed. The motor can be further miniaturized and it has potential to be applied to medical microrobots, endoscopes or micro laparoscopic devices, and cell manipulation devices.

In this study, K 0.5 Na 0.5 NbO 3 + 0.25 mol% MnO 2 + 0.38 mol% K 5.4 Cu 1.3 Ta 10 O 29 lead-free piezoelectric ceramics were prepared by a conventional ceramic sintering technique and fabricated into a square-plate contour-vibration-mode piezoelectric transformer. The ceramic was well sintered to a dense structure at 1110 • C. Because of the pinning effects provided by the defect dipoles, the ceramic exhibited excellent 'hard' piezoelectric characteristics: d 33 = 90 pC N −1 , k p = 0.40, ε r = 300, tan δ = 0.003 and Q m = 1900. The piezoelectric transformer showed a maximum power density of 10 W cm −3 with a temperature rise of 20 • C. When operated with a matching load of 8 k , the maximum efficiency of the transformer reached 96%. The transformer has great potential to be used in power supply units and other electronic circuits.

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