Confirmation of ionization mechanism of electrical breakdown in polymers

A long-standing debate in dielectric physics is how neutral molecules lose electrons, and it haspitted the hypothesis of impact ionization against the hypothesis of field ionization of molecules. Since impact ionization can’t explain the electrical breakdown of polymers, Pakhotin et al. looked into field ionization, which, unlike the former, can occur without external injection.

The researchers tested polyethylene terephthalate films, exposing them to large negative voltage pulses and measuring the exact moment of breakdown with an oscilloscope. Developing computational calculations to describe the aging and description of the polymers, the researchers created a model to calculate the lifetime of the polymers. Since different barrier shapes effect electron tunneling, the team did calculations for both triangular and Coulomb barriers, though Coulomb barriers were found to be more suitable for the polymer durability calculations.

Using the experimental data, they verified the lifetime parameters of the polyethylene terephthalate. The results confirmed field ionization as the ionization mechanism of electrical breakdown in polymers.

“The resulting equations for the lifetime lines allow us to predict the exact field strength at which a lifetime jump will occur for a specific polymer, given its parameters,” said author Vladimir Pakhotin. “In practice, this will allow engineers to more accurately calculate the operating limits and lifespan of thin-film capacitors and cable insulation.”

Pakhotin notes it is important to test other dielectrics, like polypropylene, to demonstrate the mechanism’s universality. He and his colleagues intended to extend the model and experiments to higher temperature ranges and include the effects of mechanical stress.

Source: “Ionization mechanism of electrical breakdown in polymers. Effect of potential barrier shape and charge mobility,” by V. A. Pakhotin, S. E. Semenov, and N. T. Sudar, Journal of Applied Physics (2026). The article can be accessed at https://doi.org/10.1063/5.0350895 .