Third Order Nonlinear Dielectric Permitivities of Ferroelectric Ceramic/VDF-TrFE 0-3 Composite Materials

A system for measuring nonlinear dielectric permittivity has been set up. The third order nonlinear dielectric permittivities of ferroelectric ceramic (PT, BT, PZT)/VDF-TrFE 0-3 composite thick films have been measured at the electric field ranging from 1 to 10 \mathrmMV / \mathrmm f₀=1 kHz and at the temperature ranging from ambient temperature to 140^\circ \mathrmC. It is found that the third order dielectric permittivity \varepsilon_3 of three kinds of composite increases with the increase of ceramic volume fraction \phi \varepsilon_3 of the composite also shows a dependence on electric field. A higher electric field produces a lower \varepsilon_3, but \mathrmBT / \mathrmP\mathrmVDF(70)-\operatornameTrFE(30) and PZT/ \mathrmP\mathrmVDF(77)-\operatornameTrFE(23) whose \phi is higher than 0.4 show a minimum at 6 \mathrmMV / \mathrmm of electric field. \varepsilon_3 of the composite which two phases being poled is less than that of the composite which only the ceramic phase being poled. The temperature spectra of \varepsilon_3 for PZT/PVDF (77) \operatornameTrFE(23) also produces an apparent thermal hysteresis phenomenon similar to that of \varepsilon_1.