Electroacoustic response of 1-3 piezocomposite transducers for high power applications

Abstract

The electroacoustic performance of 1-3 piezoelectric composite transducers with low loss polymer filler was studied and compared to monolithic Pb(Zr,Ti)O 3 (PZT) piezoelectric transducers. The 1-3 composite transducers exhibited significantly high electromechanical coupling factor (k t $ 0.64) when compared to monolithic counterparts (k t $ 0.5), leading to the improved bandwidth and loop sensitivity, being on the order of 67% and À24.0 dB versus 44% and À24.8 dB, respectively. In addition, the acoustic output power and transmit efficiency ($50%) were found to be comparable to the monolithic PZT transducers, demonstrating potential for broad bandwidth, high power ultrasonic transducer applications. V C 2012 American Institute of Physics.[http://dx.doi.org/10.1063/1.4772482] Piezoelectric transducers are widely employed in a range of medical applications, including ultrasound diagnostic imaging and ultrasound therapy. Ultrasound imaging is one of the most widely used imaging modalities due to the capability of a non-invasive visualization of interior tissues in real time with high resolution.1 Recently, ultrasound has attracted attention for therapeutic applications, specifically ultrasound guided high intensity focused ultrasound (HIFU) therapy, as it allows for thermal ablation of malignant and benign tumors without open surgery. 2-5The main differences between ultrasound imaging and therapeutic applications are operating frequency and power level. Megahertz or above ultrasound is usually used for diagnostic imaging as the image resolution is proportional to operating frequency. The acoustic power and intensity levels are relatively low, being on the order of 0.05 W and 1-2 W/cm 2 , respectively, in order to prevent the tissue damage. In contrast, the acoustic power and intensity levels of therapeutic ultrasound, such as HIFU, are several orders of magnitude greater, typically being on the order of 10-300 W and 1000 to 20,000 W/cm 2 , with operating frequencies in the range of 0.8 MHz to 2 MHz. General characteristics of the ultrasound used for different therapeutic applications, such as frequency and acoustic intensity, are summarized in Fig. 1. 6 For the generation of high power ultrasound, high electromechanical coupling k ij and mechanical quality factor Q m of piezoelectric transducers are desired, where the high electromechanical coupling factor permits effective energy conversion from electrical energy to mechanical energy, while the high mechanical quality factor reduces heat generation under high power operation. The electroacoustic power efficiency is also improved with increasing vibration velocity (v) of a piezoelectric material, which is related to the acoustic output power, and proportional to the product of electromechanical coupling and mechanical quality factor. 7Piezoelectric/polymer composites with 1-3 connectivity offer several advantages over monolithic ceramics for medical ultrasonic transducers, with high electromechanical coupling (k ij ), low spurious modes, and flexibility in terms o...

Flexible 1-3 Piezoelectric Composites with Soft Embedded Conductive Interconnects for Underwater Acoustic Transducers

“…In addition, the parameters e 33 d 33 and g 33 d 33 are 4724.6 pC/mV and 24.8 pm 2 /N, respectively. Compared with the FOM of 1-3 composites previously reported, ,,, the FOM in this work is higher (Figure f). It shows that the transducer equipped with the PSC has high a performance transceiver and higher competitiveness among the existing transducers.…”

“…The d 33 values and average value of 60 random points are obtained (Figure d), where the average value is 489.4 pC/N. Compared with the previously reported rigid composites, ,,,, the d 33 in this work is higher, indicating that the PSC has better piezoelectric properties (Figure e). The underwater acoustic transducers based on the PSC show higher transmitting and receiving response.…”

“…(c) Comparison of k t with previously reported 1-3 composites. ,,,,− (d) Comparison of d 33 with previously reported 1-3 composites. ,,,, (e) d 33 values and the average value of 60 points. (f) Comparison of FOM with previously reported 1-3 composites. ,,, …”

“…Table shows the comparison of the main properties between the PSC and the rigid 1-3 composites. Compared with the k t of the rigid 1-3 composite (Figure c), ,,,,− the PSC had a higher k t , indicating a higher energy conversion efficiency of electrical and mechanical energy. This was mainly due to the fact that silicone rubber is softer than epoxy resin, which reduces the mechanical constraint on the piezoelectric material and enables the piezoelectric column to exhibit a better 33-mode, thus improving the radiating ability of sound energy.…”

Parametric Analysis and Optimization of Radially Layered Cylindrical Piezoceramic/Epoxy Composite Transducers

“…These composites can overcome the shortcomings of single-phase piezoelectric materials, such as brittleness, high acoustic impedance, and at the same time possess the advantages of both the piezoceramics and the polymers, including low acoustic impedance, high electromechanical coupling coefficient, low mechanical loss and large dielectric constant [ 8 , 9 ]. Through designing and optimizing various connectivity patterns, such as 1-3 type [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ], 2-2 type [ 3 , 19 , 20 , 21 ], these transducers can be used in high-frequency, high-power, and high-temperature applications [ 9 ]. In addition, an addition of modified epoxy, i.e., aluminum load epoxy, can also enhance their dielectric, piezoelectric and acoustic dampening [ 22 , 23 , 24 ], which is very useful for structural health monitoring, energy harvesting, and acoustic liners [ 22 ].…”