Measurement of spatial electric field distribution in polymer films by using an acoustic step-wave probing technique

An acoustic step-wave probing technique was used to investigate the electric field distribution in insulating materials subjected to a high DC electric stress. The acoustic step pressure was generated by applying a high-voltage step (rise time <10 ns to 3 kV) to a piezoelectric transducer of LiNbO/sub 3/. The deconvolution technique was used to process the output acoustic signal, because this signal does not represent the profile of the electric field distribution in a sample directly. The electric field distortion in the sample was observed as a function time for two different parameters: electric field intensity (10/sup 4/-10/sup 5/ V/cm), and temperature of the samples (20-85 degrees C). The results indicate that no distortion of electric field occurred for either of the applied voltages when the sample was maintained at room temperature. On the other hand, when the sample temperature was increased to greater than about 55 degrees C, distortion of the electric fields was clearly observed.<>