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 MV/m (f0= 1kHz) and at the temperature ranging from ambient temperature to 140℃ . It is found that the third order dielectric permittivity ε3 of three kinds of composite increases with the increase of ceramic volume fraction φ ε3 of the composite also shows a dependence on electric field. A higher electric field produces a lower ε3, but BT/PVDF(70)-TrFE(30) and PZT/PVDF(77)-TrFE(23) whose φ is higher than 0.4 show a minimum at 6MV/m of electric field.ε3 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 ε3 for PZT/PVDF(77)-TrFE(23) also produces an apparent thermal hysteresis phenomenon similar to that of ε1.