Abstract
Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN–PMN–PT) piezoelectric single-crystal rectangular beams with the PIN:PMN:PT ratio of 0.33:0.35:0.32 are prepared, and their mode-coupling effect is investigated both theoretically and experimentally for ultrasonic array transducer applications. The PIN–PMN–PT rectangular beams become a tall-narrow beam and a short-wide plate, and so exhibiting an uncoupled height-extensional (beam) mode and an uncoupled thickness-extensional (plate) mode, at a width-to-height ratio G (= L / H) of 6.0, respectively. With G varying in the range of 1.6 to 3.1, the beam mode not only couples strongly with the width (lateral) mode, but also coexists obviously with the plate mode, giving high electromechanical coupling coefficients k_33^' and k_t of ~0.75 and ~0.50, respectively. With the guide of the mode-coupling results, a multifrequency ultrasonic array transducer having three distinct operational frequencies of 1.52, 2.60, and 6.01 MHz, corresponding to the coupled/coexistent beam mode, lateral mode, and plate mode, respectively, is developed using a mode-coupled rectangular beam of G = 1.6. Two different single-frequency ultrasonic array transducers, fabricated using two different uncoupled rectangular beams, one operating in uncoupled beam mode with G = 0.6 at 2.24 MHz and one working in uncoupled plate mode with G = 10.0 at 5.75 MHz, are also developed for comparison.
Highlights
Longitudinal wave ultrasonic transducers are widely used in medical ultrasonic imaging, nondestructive evaluation, underwater sonar, and so on
The beam mode frequency f H1 is essentially determined by the height H of the PIN–PMN–PT rectangular beams
To prepare [001]-poled PIN–PMN–PT rectangular beams with a constant height H but with different widths L and different G (=L/H), the [001]-poled PIN–PMN–PT rectangular plates were diced along the width in the [100] direction using an 0.20 mm-thick nickel/diamond dicing blade mounted on a DAD 321 dicing saw (Disco Corp., Tokyo, Japan) (Figure 1)
Summary
Longitudinal wave ultrasonic transducers are widely used in medical ultrasonic imaging, nondestructive evaluation, underwater sonar, and so on. The uncoupled beam mode in the piezoelectric rectangular beams has been utilized to facilitate high sensitivity and wide bandwidth in single-frequency ultrasonic array transducers [4,5]. Based on the results of mode coupling, a multifrequency ultrasonic array transducer is developed using a mode-coupled rectangular beam of G = 1.6 to excite three coupled/coexistent operational modes, namely beam mode, lateral mode, and plate mode, at three different operational frequencies of 1.52, 2.60, and 6.01 MHz, respectively. The performance of the multifrequency ultrasonic array transducer is evaluated and compared with those of two different single-frequency ultrasonic array transducers having two different uncoupled rectangular beams to respectively enable an uncoupled beam mode with G = 0.6 at 2.24 MHz and an uncoupled plate mode with G = 10.0 at 5.75 MHz
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