Effect of pore size and porosity on piezoelectric and acoustic properties of Pb(Zr0.53Ti0.47)O3 ceramics

We studied the effect of porosity and pore morphology on the functional properties of Pb(Zr0.53Ti0.47)O-3 (PZT) ceramics for application in high frequency ultrasound transducers. By sintering a powder mixture of PZT and polymethylmetacrylate spherical particles (1.5 and 10 mu m) at 1080 degrees C, we prepared ceramics with similar to 30% porosity with interconnected micrometer sized pores and with predominantly similar to 8 mu m spherical pores. The acoustic impedance was similar to 15 MRa for both samples, which was lower than for the dense PZT. The attenuation coefficient alpha (at 2.25 MHz) was higher for ceramics with similar to 8 mu m pores (0.96 dB mu m(-1) MHz(-1)), in comparison to the ceramic with smaller pores (0.56 dB mu m(-1) MHz(-1)). The high alpha value enables the miniaturisation of the transducer, which is crucial for medical imaging probes. The dielectric and piezoelectric coefficients, polarisation, and strain response decreased with increased porosity and decreased pore/grain size. We suggest a possible role of pore/grain size on the switching behaviour.