Piezoelectric ceramic fibre/polymer 1-3 composites for transducer applications.

摘要

Three kinds of bulk ceramics and ceramic fibres were fabricated using the sol-gel method. Their compositions are Pb(Zn_1/3Nb_2/3) _0.30(Zr_0.52Ti_0.48)_0.70O ₃ [PZN-PZT], Pb_0.85Sm_0.1Ti_0.98Mn _0.02O₃[PSmT] and Pb(Li_1/4Nb_3/4) _0.01(Mn_1/3Nb_2/3)_0.06Zr_0.46Ti _0.47O₃ [PLN-PMN-PZT]. PSmT ceramic shows a large piezoelectric anisotropy (k_t/k_p ∼ 10), has a piezoelectric constant d₃₃ of 51 pC/N, electromechanical coupling coefficient k_t of 0.44, k_p 0.05 and Q_m of ∼561. PZN-PZT is a “soft” PZT ceramic, which has a d₃₃ of ∼600 pC/N, k_t of 0.48, k_p of 0.61 and Q_m of ∼65. PLN-PMN-PZT is a “hard” PZT ceramic, which has a d₃₃ of 315 pC/N, k_t of 0.50, k_p of 0.59 and a high Q _m of 1675.; Three types of ceramic fibres were fabricated by a gel-spinning technique. After proper heat treatment, they were found to have properties similar to that of the bulk ceramics. Their morphology had also been examined with scanning electron microscopy.; Using epoxy as a matrix, three kinds of fibre/epoxy 1-3 composites were fabricated. These composites were fabricated into disks; and the disks were ground, polarized and then characterized. The results show that the length/width ratio of the fibres in PSmT fibre/epoxy 1-3 composites does not play an important role in the disk vibrations because PSmT has a low k_p.; In order to prevent the coupling between the lateral resonance of the individual fibre and the thickness resonance of the 1-3 composites, fine PZN-PZT ceramic fibres with a diameter of 25 μm were used. The 1-3 composites disks fabricated from these fine ceramic fibres have a pure thickness resonance peak. The k_t values of the PZN-PZT 1-3 composites with ceramic volume fraction ranging from 0.25 to 0.62, are normally larger than the k _t, and are close to the k₃₃ of the bulk ceramics.; The PLN-PMN-PZT fibre/epoxy 1-3 composites fabricated from 50 μn diameter ceramic fibres were used in low frequency transducer fabrication (∼10 MHz). The k_t values of this 1-3 composite with ceramic volume fraction, ranging from 0.25 to 0.45, are also larger than the k_t, but close to the k₃₃ of the bulk ceramics.; Some concave 1-3 composite disks with non-uniform thickness were fabricated. Their k_t values were found to be higher than that of the disks with a uniform thickness and with the same ceramic fibre loading.; Transducers for medical imaging were assembled from the three kinds of ceramic fibre/epoxy 1-3 composites and their bandwidth, centre frequency, insertion loss, k_t and beam profile were measured. (Abstract shortened by UMI.)