The dipolar α peak and space charge ρ peak in the electrical polarized materials

The nature of the thermally stimulated discharge current peaks in 6 μm thick biaxially stretched polyethylene terephthalate films was investigated. Alternating current measurements have been used for the investigation of the coupling between dipolar charge and space charge. The activation energy was determined using the initial rising method and the whole curve method. The values obtained are generally lower than the values for β dielectric relaxation and are associated with charge released from shallow traps. The values obtained by the whole curve method are higher and increase as the charge that flows through the circuit increases. It seems that these values follow a compensation law and the compensation temperature is in good agreement with the Vogel temperature determined from ac measurements. The conclusion is that even the peak at the glass-rubber transition temperature region is mainly determined by the coupling between dipolar and space charge