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

This paper reports on the fabrication and characterization of fine scale piezoelectric composites with 1-3 connectivity using fibers derived from a metal alkoxide sol-gel process. Using this technique, pure thickness mode resonance for this type of composite has been increased from 15 MHz up to 70 MHz by maintaining pillar aspect ratio requirements. Piezoceramic fibers of Nb or La modified lead zirconate titanate (PZT) were produced with final diameters ranging from 15 to 50 μm. Composites having 1-3 connectivity were produced using the fibers as pillars. Composites could be fabricated with volume fractions from 10 to 45% allowing tailoring of both the dielectric constant and acoustic impedance without degrading coupling. Dielectric constant, polarization and coercive field values varied slightly from bulk values due to clamping by the polymer matrix, increasing as the fiber diameter decreased. Composites with resonance frequencies ranging from 15 to 70 MHz were studied. The thickness dependence of the properties gave indications to radial mode/thickness mode interactions at pillar aspect ratios near 1.7 to 1 thickness to diameter. Coupling coefficients (k_t) from 58% to 73% with mechanical quality factors <15 were detected.