Effect of gamma-ray irradiation on the TSC in polyethersulfone

When polyethersulfone was irradiated by /spl gamma/ rays and then poled at 37/spl deg/C, a new TSC (thermally stimulated current) peak appeared at /spl sim/100/spl deg/C. This new peak and other peaks near 40 and 150/spl deg/C increase with an increase in dose of /spl sim/0.6 kGy, and this is considered to be due to trapped charges and other ionic carriers becoming mobile when rearrangement of scissioned chains occurs. However, if the dose exceeds 0.6 kGy, the peak magnitude decreases. Furthermore, if the TSC was poled at 120/spl deg/C, only the peak near 150/spl deg/C appeared and this peak monotonically decreased with an increase in the irradiation dose. A similar decreasing tendency was also observed in the conduction current and in the residual voltage. These decreasing features are considered to be caused by the radiation-induced change that rearrangement of scissioned chains decreases free volume for ionic transport.