TEMPERATURE-DEPENDENCE OF THE ELECTROMECHANICAL PROPERTIES OF 0-3 PBTIO3-POLYMER PIEZOELECTRIC COMPOSITE-MATERIALS

The electromechanical properties of 0-3 ceramic-polymer composite piezoelectric materials manufactured by NTK Corporation in Japan have been measured as a function of temperature using several techniques. The elastic, dielectric, and piezoelectric constants were measured by fitting the complex admittance vs frequency spectrum to a model of a piezoelectric resonator near the electromechanical resonance [Xu et al., J. Wave Mater. Interact. 2, 105-181 (1987)]. These properties are shown to vary significantly with temperature as a result of the glass-transition region of the polymer phase. The theory of viscoelasticity in polymers discussed by Ferry (WLF theory), which explains the influence of the glass transition on the elastic properties of polymers, is used to describe the temperature dependence of the elastic and dielectric properties of the composite materials. The temperature dependence of the dielectric permittivity is shown to be similar in form to the temperature dependence of the elastic properties. For a material with larger filler particles, the temperature dependence corresponds exactly. For materials containing smaller particles, the magnitude of the time-temperature superposition shift parameters are not consistent for the different properties. The application of the time-temperature superposition principle for shifting experimental data to account for differences in measurement frequencies and temperatures is demonstrated. These measurements are compared with independent elastic property measurements and with results from thermal analysis. They ace found to be consistent. Values for Poisson's ratio are calculated using independent measurements of the elastic constants S-11(E) and C-33(D). The observed properties can be related to the structure of the composite material.