On the interpretation of some electrical aging and relaxation phenomena in solid dielectrics

Electrical aging and relaxations of solid dielectrics are phenomena studied for decades but still largely poorly understood. In this paper, we show that some of the theories often cited in the literature are wrong or inappropriate. The relations between aging, space charges and polarization of polyethylene (PE) under the influence of high electrical fields (above 20 kV/mm) are discussed in light of our electrical aging model. Below a so-called critical field, the activation volume of the aging process is dependent on the field-induced strain. It is our contention that strong charge injection occurs only after nanocavity formation, i.e. above the critical field. The amorphous phase is then significantly deformed and weak van der Waals bonds are broken, leading to another faster aging regime. The possible relation between the nanocavity formation at moderate fields and bonds breaking at higher fields proposed in our aging model and various polarization measurements is discussed. One objective of this paper is to encourage the development of more complex and complete theories specific to dielectrics. Some experimental work needed to achieve this goal is pointed out.