High Field Conduction in Biaxially Oriented Polypropylene at Elevated Temperature

Although biaxially-oriented polypropylene thin film is a common dielectric for many high voltage pulsed power capacitor applications, the electrical conductivity under high field at elevated temperature is mostly unknown. Such knowledge is valuable not only for better understanding of the origin and transport mechanisms of the charge species at high field, but also for gaining insight for improving breakdown strength and electro-thermal modeling of high energy density, pulsed power capacitors. In this work, the conduction mechanism was investigated and the conductivities near breakdown were inferred through the use of a thermal runaway criterion and the measured breakdown strength at various temperatures. Results suggested that conduction is by hopping with a thermal activation energy that is about 0.76 eV and is field-independent. Such finding allows the use of an Arrhenius term and a field-dependent term to describe the field-dependent conductivity up to breakdown.