Degradation of the dielectric and piezoelectric response of b-poly(vinylidene fluoride) after temperature annealing

Abstract

The effect of annealing temperature and time on the dielectric and piezoelectric response of poly(vinylidene fluoride), PVDF, has been studied. The observed decrease in the value of the dielectric, έ, and piezoelectric, d33, constants is related to depoling of the material and not to variations of the degree of crystallinity or the electroactive β-phase content. In a general way, the dielectric and piezoelectric responses decrease strongly in the first four hours at a given temperature, in particular for temperatures higher that 80 ºC, reaching stable values for longer annealing times. For most applications, the temperature of 100 ºC will set the limit of suitable performance. Nevertheless, the material still retains stable piezoelectric response of ~ 4 pC/N after reaching temperatures of 140 ºC. The mechanisms behind the observed behavior have been discussed