Thermal aging of pyroelectricity in PVDF and P(VDF-TrFE) copolymers

Laurent Ibos; G. Teyssedre; A. Bernes; C. Lacabanne

doi:10.1117/12.373716

14 December 1999 Thermal aging of pyroelectricity in PVDF and P(VDF-TrFE) copolymers

Laurent Ibos, G. Teyssedre, A. Bernes, C. Lacabanne

Proceedings Volume 4017, Polymers and Liquid Crystals; (1999) https://doi.org/10.1117/12.373716
Event: International Conference on Dielectric and Related Phenomena '98, 1998, Szczyrk, Poland

Abstract

A study of the thermal aging of the pyroelectric properties of commercially available bioriented PVDF and P(VDF-TrFE) 75-25 mol percent films is reported. The analysis of pyrocurrent spectra has been carried out in a large temperature range of -100 degrees C up to +150 degrees C. The pyroelectric coefficient p₃ shows a distinct temperature dependence below and above thermal transitions, and especially the glass transition. We consider how this dependence changes upon aging. The influence of both aging temperature and aging time was investigated. ThermoStimulated Currents spectroscopy (TSC) has been used as a complementary technique of investigation. We have paid a particular attention to the evolution of the relaxation modes associated with the glass transition and with the (alpha) _c transition as a function of aging conditions. Experimental results of (beta) -PVDF show that the decay of the pyroelectric activity is linearly dependent on the annealing temperature. Identical aging conditions induce a lower decay of p₃ in P(VDF-TrFE) 75-25 than in PVDF, attesting the higher stability of the macroscopic polarization in fluorinated copolymers. The evolution of the decay of p₃ as a function of the aging time is more complex. Indeed, p₃ decreases quickly below a short characteristic aging time, and much slower at longer times. This characteristic time is aging temperature dependent. The evolution of the relaxation mode association with the glass transition shows that irreversible crystallinity changes occur at aging temperature higher than +110 degrees C. So, crystallization phenomena do not play a major role in the decay of p₃. Besides, the (alpha) _c transition seems to play an important role in the aging of pyroelectricity. Indeed, any loss of pyroelectric activity is detected after aging at temperatures lower than the (alpha) _c transition.

Citation Download Citation

Laurent Ibos, G. Teyssedre, A. Bernes, and C. Lacabanne "Thermal aging of pyroelectricity in PVDF and P(VDF-TrFE) copolymers", Proc. SPIE 4017, Polymers and Liquid Crystals, (14 December 1999); https://doi.org/10.1117/12.373716

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