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

Barium modified bismuth sodium titanate, 0.94(Bi0.5Na0.5) TiO3-0.06BaTiO(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 mum. The grain size of the ceramic fibers is 2-3 mum. The fibers were then incorporated into an epoxy matrix to form 1-3 composites with about 0.30-0.40 volume fraction (nu(f)) of BNBT-6 ceramics. After poling, piezoelectric and dielectric properties of the 1-3 composites were measured using an impedance analyzer HP4294A. With similar to0.30 ceramic fiber volume fraction, the electromechanical coupling coefficient k(t) is 0.71 for the sol-gel fiber/epoxy composite. A nu(f) = 0.30 composite was subsequently thinned down to 143 mum 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. (C) 2004 Elsevier B.V. All rights reserved.