Charge decay of corona‐charged electrets of amorphous polyethylene terephthalate

During the formation of corona‐charged electrets of amorphous poly(ethylene terephthalate) at T p between room temperature and 100°C, the charge injected from the electrodes to the sample is trapped from T p to temperatures higher than 100°C. This fact determines that the measure of the initial charge of the electret is homocharge which is unstable with the time. The stored charge in the deep levels is the main cause for the internal field limiting the decrease of the heterocharge which finishes dominating in the decay process. The application of the thermally stimulated discharge to these electrets gives three relaxations whose behaviour has been analysed and has helped to interpret the decay of the charge.