High frequency ultrasonic transducer with KNN/BNT 0–3 composite active element

High frequency ultrasonic transducer with operating frequency over 200 MHz has been fabricated using a composite sol gel technique. Piezoelectric lead-free thick film was prepared by dispersing the crystalline fine KNN powder into BNT precursor solution to form composite slurry which was spin-coated on the platinum buffered Si substrate. The resultant KNN/BNT film with thickness of 8 μm exhibited good dielectric and ferroelectric properties. A single element focused transducer with an f-number of 3 based on this composite film was built by conventional transducer technology and silicon etching process. The measured center frequency and the bandwidth at -6dB were 225 MHz and 68 MHz, respectively. Wire phantom imaging acquired by the composite transducer was also presented and spatial resolutions were assessed.