New processing of porous PZT ceramics with high connectivity was investigated using capsule-free O2 HIP technology. Porous PZT bodies were prepared by pressureless-sintering of green compacts with various amounts of spherical PMMA particles, followed by hot isostatically pressed at 1100°C and 200 MPa for 1 hour in 5%O2/Ar mixture gas atmosphere. The densification of porous PZT sintered bodies hardly occurred by capsule-free O2 treatment, resulting in the formation of well-developed neck growth between PZT grains. They exhibted a homogeneous microstructure with a bimodal pore size distribution consisting of both several ¼m and 50–80¼m pore sizes.
The capsule-free O2 HIPed porous PZT bodies have a larger permittivity and a smaller depolarizing factor about a half than the specimens before O2 -HIPing, suggesting that the HIPed PZT has a higher connectivity. Piezoelectric g33 constant-porosity relations were also described and mechanical property was discussed to indicate an increase of bending strength more than 20% compared to conventional sintering.