Processing and properties of 15-70 MHz 1-3 PZT fiber/polymer composites

This paper reports on the fabrication and characterization of fine scale pi ezoelectric composites with 1-3 connectivity using fibers derived from a me tal alkoxide sol-gel process. Using this technique, pure thickness mode res onance for this type of composite has been increased from 15 MHz up to 70 M Hz by maintaining pillar aspect ratio requirements. Piezoceramic fibers of Nb or La modified lead zirconate titanate (PZT) were produced with final di ameters ranging from 15 to 50 mum. Composites having 1-3 connectivity were produced using the fibers as pillars. Composites could be fabricated with v olume fractions from 10 to 45% allowing tailoring of both the dielectric co nstant and acoustic impedance without degrading coupling. Dielectric consta nt, polarization and coercive field values varied slightly From bulk values due to clamping by the polymer matrix, increasing as the fiber diameter de creased. Composites with resonance frequencies ranging from 15 to 70 MHz. w ere studied. The thickness dependence of the properties gave indications to radial mode/thickness mode interactions at pillar aspect ratios near 1.7 t o 1 thickness to diameter. Coupling coefficients (kt) from 58% to 73% with mechanical quality factors <15 were detected.