Changes of space charge profiles in PET electrets after thermally stimulated discharges

Behaviour of electric charges in a PET film has been investigated under the condition of partial discharging at higher annealing temperatures. The PET electrets corona-charged at room temperature and 440 K were investigated. The step electroacoustic method was used for the measurement of the space charge distributions along the sample thickness. The highest surface charge densities, and charge stability were obtained after negative corona charging at 440 K.