For the terpolymer investigated here, there is no sign in the dielectric spectra of an F-P transition (Fig. 12). There is no hysteresis in the dielectric data when mea-sured in heating and in cooling. On the other hand, for terpolymers with lower CFE concentration or non-uniform CFE distribution in the terpolymer, large coherent polar-domains and a relaxor phase coexist, and a frequency-independent phase transition process is ob-served in both ε and ε spectra, although it is shifted to lower temperatures [17]. In previous studies on high-energyelectronirradiatedcopolymers,similarincomplete normal-relaxor conversionhasalso beenobservedin sam-ples with insufficient irradiation treatment of the P(VDF-TrFE) copolymer [7, 8, 34]. However, increasing the ir-radiation dosage eliminates the ferroelectric phase in the copolymer and hence there is no sign of F-P phase tran-sition process in the dielectric spectra in these properly treated copolymers [7].
It is interesting to note that in the same temperature range as the βa process in the normal ferroelectric copolymer, a strong dielectric dispersion (denoted as βr) is observed in the relaxor terpolymer, which follows the Vogel-Fulcher law Figs 12 and 13, with f0 = 987 MHz,U = 3.86 kJ/mol = 0.0400 eV, and T0 = 244.3 K. However, this relaxation process exhibits a significantly larger increase in dielectric constant