Abstract: In this paper,the charge-decay of polyproplene (PP) film electrets is analysed.It is shown that the hopping of intrinsic carriers impelled by internal field is the main reason for potential-decay.The average hopping stop-distance calculated from the test data is about the order of 10^-8 m. This result has been demonstrated by the X-ray diffraction of the film recently.

Key words: polymer, decay, Xray diffraction, eleetret