High frequency 1-3 composite transducer fabricated using sol–gel derived lead-free BNBT fibers

Abstract

Barium modified bismuth sodium titanate, 0.94(Bi 0.5Na 0.5) TiO 3–0.06BaTiO 3 (BNBT-6), fine scale piezoelectric fibers were fabricated using a sol–gel technique. The diameter of the sintered BNBT-6 fibers is less than 100 μm. The grain size of the ceramic fibers is 2–3 μm. The fibers were then incorporated into an epoxy matrix to form 1-3 composites with about 0.30–0.40 volume fraction ( v f) of BNBT-6 ceramics. After poling, piezoelectric and dielectric properties of the 1-3 composites were measured using an impedance analyzer HP4294A. With ∼0.30 ceramic fiber volume fraction, the electromechanical coupling coefficient k t is 0.71 for the sol–gel fiber/epoxy composite. A v f=0.30 composite was subsequently thinned down to 143 μm thickness and constructed into an ultrasonic transducer. The pulse-echo response, bandwidth (BW), and insertion loss (IL) of the transducers were studied. This sol–gel fiber composite transducer can be operated at a higher frequency of 14.30 MHz with a bandwidth of 80%. The good transducer performance indicated that the BNBT-6 fiber/epoxy 1-3 composite has potential in medical imaging applications.