Effects of Humidity on the Microstructure and the Ferroelectric Properties of Sol-Gel grown P(VDF-TrFE) Films

초록

We report the microstructure and the ferroelectric properties of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] films grown under various humidity conditions and synthesis times by using a sol-gel method. When the synthesis time under a humid condition was short (approximately 30 min), the moisture in the environment affected only the surface morphology without any loss of ferroelectricity for the P(VDF-TrFE) films. In contrast, when the synthesis time was long (approximately 90 min), the moisture strongly affected the microstructure and the ferroelectric properties of P(VDF-TrFE). The transparent P(VDF-TrFE) film became opaque at high humidity. Scanning electron microscopy revealed numerous pores on the surface of and inside the film. The pores reduced the Young's modulus considerably from 4.15 to 0.97 GPa for the films grown at 20 and 80% relative humidity, respectively. In addition, the ferroelectric hysteresis loop disappeared at humidities above 60%. This work provides upper limits for the humidity and the synthesis time for the growth of high-quality P(VDF-TrFE) films by using a sol-gel method.

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