4. Conclusio n
In this work, particle-stabilized foams and the gelcasting
technique were combined to produce porous PZT ceramics. By
varying the concentrations of valeric acid and pH values of
final suspension, wet foams with different foaming capacities
were prepared, while the porosity and microstructure of
sintered specimens changed accordingly. As for the dielectric
and piezoelectric properties, the values of εr and d33 of porous
PZT ceramics not only decreased with increasing porosity, but
also were affected by the shape or structure of pores. The value
of dh increased moderately with the increase of porosity, which
allowed the porous PZT ceramics to have high HFOM values.
The sample with a porosity of 76.3% showed a HFOM value
of as high as 19520 10 −15 Pa−1. The acoustic impedance
decreased almost linearly with increasing porosity, and reached
the lowest value of 1.35 Mrayl, so the porous material of this
kind is suitable for the design of underwater hydrophone.