CaBi₄Ti₄O₁₅-based lead-free sol–gel composites for high-temperature application

Abstract

CaBi4Ti4O15 (CBiT)-based lead-free sol–gel composites were developed for high-temperature ultrasonic transducer application. In this study, two types of lead-free sol–gel solution, Ba0.7Sr0.3TiO3 (BST) and Bi4Ti3O12 (BiT), were used for consistency to fabricate ∼50-µm-thick CBiT/BST and CBiT/BiT films on 3-mm-thick titanium substrates by a sol–gel spray technique. BST and BiT were chosen because of their high dielectric constant and high Curie temperature, respectively, in addition to their being lead-free materials. A thermal cycle test was carried out between RT and 600 °C, and clear multiple echoes were confirmed during three thermal cycles for both materials. In addition, the sensitivity of CBiT/BiT was higher than that of CBiT/BST although a higher poling temperature is required for CBiT/BiT. Therefore, an ultrasonic transducer potential for high-temperature application was successfully demonstrated.

Preliminary study of self-shape estimation of ultrasonic flexible probe using direct waves among elements for medical ultrasound imaging

“…For example, a flexible probe sold for NDT 5) has a pitch of 1 mm, whereas the pitch of the model used in this study was set to 2.8 mm. The proposed method assumes a flexible probe fabricated by the sol-gel composite method, [6][7][8][9][10][11][12][13][14][15][16][17] which still has a wider pitch owing to the insufficient fabrication process of the top electrodes. Models 1-4 mentioned above had a pitch of 2.8 mm, which is larger than that of a commercially available probe, so the directivity of the elements could be narrowed and the ultrasonic waves could not be irradiated perfectly spherically.…”

“…An ultrasonic flexible probe [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] can alter its shape to match the curved surface of an object as well as visualize its interior; this cannot be achieved by a linear ultrasonic probe. For example, in the field of nondestructive testing (NDT), ultrasonic probes are employed for visualizing pipe interiors, [1][2][3] which are often measured using a single plate wedge transducer.…”

Thin, flexible, and biocompatible medical ultrasound array transducer using a sol–gel composite spray technique

“…We have previously developed ultrasonic transducers using the sol-gel composite spraying (SCS) method for nondestructive testing. [17][18][19][20][21][22][23][24] This technique allows the production of flexible, thermally robust sensors with broadband acoustic properties. However, previous studies did not utilize an array structure capable of generating B-mode images, nor were they sufficiently biocompatible for medical applications.…”

Polarity effect of corona discharge poling for sol-gel composite-based ultrasonic transducers

“…1,2) The thick porous films made by solgel composite materials have helped realize ultrasonic transducers with variable center frequency (in the range of 2-50 MHz); such transducers are suitable for non-destructive testing (NDT) applications. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Owing to the porosity of solgel composite films, sol-gel composite-based ultrasonic transducers exhibit high temperature durability, curved surface applicability, reasonable signal strength, and high signalto-noise ratio (SNR), in addition to the suitable frequency range for NDT. 11,20) Therefore, sol-gel composite-based ultrasonic transducers have a good potential for industrial applications.…”