抄録
This paper describes a new direct measurement of the carrier mobility in insulating materials such as polyethylene. Polyethylene is often chemically cross linked in order to improve heat resistance, however, some cross linking by-products such as acetophenone significantly affect its electric properties. In this study, an experiment was performed to clarify how the carrier mobility is influenced by the existence of acetophenone in polyethylene. One side of a polyethylene film with 0.1-mm thick was soaked with acetophenone. Time-dependent charge distribution was monitored by the pulsed-electroacoustic method, when a "carrier excitation pulse voltage"; was superposed on a "DC bias voltage";. It was observed that a positive charge packet was injected from the anode by the excitation pulse, and moved towards the cathode being driven by the bias field. There was a good correlation between local acetophenone content and the mobility at corresponding position. It was concluded that diffusion of acetophenone leads to the increase in the mobility of the injected positive carrier, up to 3×10-10cm2/Vs. It was also proved that the carrier mobility can be estimated by this technique, even if the specimen has a gradation in its property.
