Development of lead-free single-element ultrahigh frequency (170-320MHz) ultrasonic transducers - PubMed (original) (raw)

Development of lead-free single-element ultrahigh frequency (170-320MHz) ultrasonic transducers

Kwok Ho Lam et al. Ultrasonics. 2013 Jul.

Abstract

This paper presents the design, fabrication and characterization of single-element ultrahigh frequency (UHF) ultrasonic transducers in which the center frequency ranged from 170 to 320MHz. The center frequency of >300MHz is the highest value of lead-free ceramic ultrasonic transducers ever reported. With concern in the environmental pollution of lead-based materials, the transducer elements presented in this work were lead-free K0.5Na0.5NbO3/Bi0.5Na0.5TiO3 (KNN/BNT) composite thick films. All transducers were evaluated in a pulse-echo arrangement. The measured -6dB bandwidth of the transducers ranged from 35% to 64%. With the optimized piezoelectric properties of the composite film, the insertion loss of the UHF transducers was measured and determined to range from -50 to -60dB. In addition to the pulse-echo measurement, a 6μm tungsten wire phantom was also imaged with a 205MHz transducer to demonstrate the imaging capability. The measured -6dB axial and lateral resolutions were found to be 12μm and 50μm, respectively. The transducer performance presented in this work is shown to be better or comparable to previously reported results even though the frequency is much higher.

Copyright © 2013 Elsevier B.V. All rights reserved.

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Figures

Figure 1

Figure 1

Schematic diagram of the transducer.

Figure 2

Figure 2

Photograph of the final transducer prototype.

Figure 3

Figure 3

Time-domain pulse/echo response and frequency spectrum for the (a) 171-MHz, (b) 205-MHz, (c) 224-MHz, (d) 278-MHz, and (e) 324-MHz ultrasonic transducers.

Figure 3

Figure 3

Time-domain pulse/echo response and frequency spectrum for the (a) 171-MHz, (b) 205-MHz, (c) 224-MHz, (d) 278-MHz, and (e) 324-MHz ultrasonic transducers.

Figure 3

Figure 3

Time-domain pulse/echo response and frequency spectrum for the (a) 171-MHz, (b) 205-MHz, (c) 224-MHz, (d) 278-MHz, and (e) 324-MHz ultrasonic transducers.

Figure 3

Figure 3

Time-domain pulse/echo response and frequency spectrum for the (a) 171-MHz, (b) 205-MHz, (c) 224-MHz, (d) 278-MHz, and (e) 324-MHz ultrasonic transducers.

Figure 3

Figure 3

Time-domain pulse/echo response and frequency spectrum for the (a) 171-MHz, (b) 205-MHz, (c) 224-MHz, (d) 278-MHz, and (e) 324-MHz ultrasonic transducers.

Figure 4

Figure 4

Modeled result of the 320-MHz composite transducer.

Figure 5

Figure 5

A wire phantom acquired by a 205-MHz plane ultrasonic transducer.

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