# Piezoelectric Composite Vibrator with a Bilaminated Structure for Bending Vibration
## 4 Fabrication and Performance Test of the Bilaminated Vibrator  
On the basis of the finite element simulation results, the 2-2 piezoelectric composite was selected to prepare a bilaminated vibrator. The ceramic vibrator with the same shape and size was also prepared in the present work to compare its performance with that of the traditional one. The 2-2 piezoelectric composite bilaminated vibrator comprised a piezoelectric phase, a polymer phase, and surface electrodes with the following structural parameters length = 49.5 mm, width = 9.5 mm, height = 2 mm, column width = 2 mm, and joint-cutting width = 0.5 mm. The PZT piezoelectric ceramic, 618 epoxy resin, and silver paste were selected as the piezoelectric phase, polymer phase, and surface electrode, respectively. The 2-2 piezoelectric composite was prepared via the \"slice and fill\" method [38; 39; 40]. The preparation process is shown in Figure 11.  
The detailed preparation procedure is described as follows [41; 42; 43]. 1. A piezoelectric ceramic block was cut into strips along the width directions of the ceramic block. The piezoelectric ceramic block was not cut through the whole thickness, and a common base was retained. The polarization direction of the piezoelectric ceramic block was parallel to the thickness direction of the ceramic. 2. The epoxy resin was cast into the piezoelectric ceramic strips. 3. The piezoelectric ceramic sample was inverted, and the ceramic base was cut precisely along the grooves between the piezoelectric ceramic strips. 4. The top and bottom surfaces of the composite were polished and cleaned using acetone, and a thin layer of silver on the surfaces as electrodes were coated via magnetron sputtering. The composite samples were fabricated in accordance with the above preparation method, as shown in Figure 12.  
Figure 11: Preparation technology of the 2-2 piezoelectric composite. Figure 10: (**a**) Admittance curves of the 2-2 piezoelectric composite bilaminated vibrator and the ceramic vibrator. (**b**) Vibration displacement curves of the 2-2 piezoelectric composite bilaminated vibrator and the ceramic vibrator. The 2-2 piezoelectric composite bilaminated vibrator is composed of two identical 2-2 piezoelectric composites bonded with epoxy resin in the opposite direction of polarity. As shown in Figure 1, the structure size of the 2-2 piezoelectric composites is \(49.5\times 9.5\times 2\) mm, and its volume fraction is 0.8 (2 mm in width of ceramic column and 0.5 mm in width of the epoxy resin). 2-2 piezoelectric composite bilaminated vibrator samples, as shown in Figure 13, were fabricated. The bilaminated piezoelectric ceramic vibrator structure (length = 49.5 mm, width = 9.5 mm, and height = 2 mm), which is made from PZT5 piezoelectric ceramic, is shown in Figure 8.  
The preparation process is shown in Figure 14. The upper and lower surfaces of the piezoelectric ceramics were polished flat, and the samples were scrubbed with alcohol. The detailed preparation procedure is described as follows. Figure 12: Image of the fabricated 2-2 piezoelectric composites. Figure 13: Image of the 2-2 piezoelectric composite bilaminated vibrator samples. 1. After drying, the samples were placed in the sample table of an ultrahigh vacuum multitarget magnetron sputtering instrument the upper surfaces were sputtered, and the samples were reversed for reverse sputtering. 2. Two identical piezoelectric ceramic vibrators were bonded with epoxy resin in the opposite direction of polarity. The piezoelectric ceramic bilaminated vibrator samples, as shown in Figure 15, were fabricated. Five groups of 2-2 piezoelectric composite bilaminated vibrator samples were tested using an Agilent 4294 A impedance analyzer. The admittance curves and impedance curves were selected to obtain the series resonance frequency \(f_{s}\) (the frequency corresponding to the maximum admittance mode) and the parallel resonance frequency\(f_{p}\) (the frequency corresponding to the maximum impedance mode). The bandwidth was also read.