Characteristic of acoustic waves generated in dielectrics under divergent electric fields

Space charge measurement under divergent electric fields can provide crucial insight into various insulating phenomena, and the space charge reconstruction relies on the relation between the measured acoustic wave and the space charge distribution if the pulsed electroacoustic method is used. However, the relation is still unclear. In this work, the characteristic of acoustic waves generated by a divergent electric field is studied. Three components of electrostatic force leading to acoustic waves, which are surface force, internal Coulomb force, and electrostrictive force, are considered. The relation between the acoustic wave and these three components is provided, and the acoustic wave characteristic is, therefore, investigated. The results show that the acoustic wave exhibits two opposite peaks for each component due to the local distribution of the force, which is different from that with a uniform electric field, and the combined waveform is greatly influenced by the contribution of electrostrictive force, making it challenging to extract space charge information.