Full set of complex material constants for porous piezoelectric ceramics

Porous piezoelectric ceramics are important for a variety of applications such as medical ultrasonic devices, non-destructive testing, underwater acoustics etc. In this paper a line of proprietary porous piezoelectric ceramics with 3-0/3-3 connectivity types were systematically studied. Complex sets of elastic, dielectric and piezoelectric coefficients of the porous piezoelectric ceramics were measured by ultrasonic and impedance spectroscopy methods using Piezoelectric Resonance Analysis (PRAP) software. Special attention was paid to the microstructure/properties interrelation and accurate determination of low-Q porous piezoelectric ceramics parameters including losses and dispersion. It was shown, that at any connectivity type and porosity up to 70 % the real structures of porous piezoelectric ceramics are close to the matrix medium structure with continuous piezoelectric ceramic skeleton. Finite element modeling of effective constants of the porous piezoelectric ceramics was performed using ANSYS software package. Critical comparison of numerical FEM calculations with the results of various approximated formulas, unit cell models and experimental data for different porous piezoelectric ceramics was carried out. Microstructural and physical mechanisms of losses in porous piezoelectric ceramics, as well as technological aspects of its large-scale manufacture and application in ultrasonic transducers were considered. A line of high-performance HIFU, NDT and medical diagnostics ultrasonic transducers made from porous piezoelectric ceramics was manufactured and tested.