Dielectric breakdown and electrical conduction of poly(vinylidene-fluoride) in high temperature region

Dielectric breakdown of poly(vinylidene-fluoride) (PVDF) is studied over the temperature range from room temperature to 150 degrees C, by applying a linearly rising voltage. The electric strength is in excess of 8 MV cm -1 at room temperature, but above 50 degrees C it rapidly falls inversely with temperature and depends on the rate of rise of the electric field but not on the sample thickness. An attempt is made to apply the impulse thermal breakdown theory to the data obtained above 50 degrees C. Assuming that the conduction is ionic the temperature rise of the sample is calculated numerically using impulse thermal breakdown theory. By fitting these theoretical electric strengths to the experimental values, the conduction parameters are estimated as follows: the activation energy is 0.9 eV, the jump distance is 9 AA and j 0 is 1.2*10 7 A m -2 .