| Three kinds of bulk ceramics and ceramic fibres were fabricated using the sol-gel method. Their compositions are Pb(Zn1/3Nb2/3) 0.30(Zr0.52Ti0.48)0.70O 3 [PZN-PZT], Pb0.85Sm0.1Ti0.98Mn 0.02O3[PSmT] and Pb(Li1/4Nb3/4) 0.01(Mn1/3Nb2/3)0.06Zr0.46Ti 0.47O3 [PLN-PMN-PZT]. PSmT ceramic shows a large piezoelectric anisotropy (kt/kp ∼ 10), has a piezoelectric constant d33 of 51 pC/N, electromechanical coupling coefficient kt of 0.44, kp < 0.05 and Qm of ∼561. PZN-PZT is a “soft” PZT ceramic, which has a d33 of ∼600 pC/N, kt of 0.48, kp of 0.61 and Qm of ∼65. PLN-PMN-PZT is a “hard” PZT ceramic, which has a d33 of 315 pC/N, kt of 0.50, kp 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 kp.; 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 kt 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 kt values of this 1-3 composite with ceramic volume fraction, ranging from 0.25 to 0.45, are also larger than the kt, but close to the k33 of the bulk ceramics.; Some concave 1-3 composite disks with non-uniform thickness were fabricated. Their kt 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, kt and beam profile were measured. (Abstract shortened by UMI.)... |
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