The dielectric constants of the PTO and PZT films before and after irradiation with various total doses as a function of frequency are shown in Fig. 5a. The dielectric constant measured at the pre-poled part of the films does not show any difference with that measured at the non-prepoled part of the films (not shown here), thus the dielectric constants of
pre-poled films are just presented in Fig. 5. It shows that the dielectric constants gradually decreased for both PTO and PZT films as the irradiation total dose increases. Fig. 5b represents the variation of the dielectric constant measured at 10 kHz in the PTO and PZT films as a function of the irradiation total dose. We found that the dielectric constant of the
PZT films significantly decreased from 850 to 580,while that of the PTO films slightly decreased from 400 to 340 as the total dose increases.