Properties of P(VDF-TeFE) thin film formed by annealing process with electric field
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1218-Z05-20
Properties of P(VDF-TeFE) thin film formed by annealing process with electric field 1
Jong-Hyeon Jeong, 1Chiharu Kimura, 1Hidemitsu Aoki, 2Masanori Okuyama and 1Takashi Sugino 1 Department of Electrical, Electronic and Information Engineering, Osaka University, Suita, Osaka, 565-0871, Japan 2 Division of Advanced Electronics and Optical Science, Osaka University, Toyonaka, Osaka, 560-8531, Japan
ABSTRACT In order to apply P(VDF-TeFE) piezoelectric polymer to micro-generator as a membrane, the polymer is deposited on a substrate by spin-coating method. In this process, some changes of properties and quality of the film are caused by a solvent which was used to dissolve the polymer granule. Since a solvent affects the film properties and surface stability, we have carried out the thermal process at a temperature higher than melting point. However, this thermal process due to a temperature higher than Curie point of the polymer causes a falling-off in electrical properties. In this paper, we have studied a method to prevent a falling-off in electric properties of P(VDFTeFE) film even though the film is annealed at a temperature higher than Curie point. INTRODUCTION For the development of portable electronic devices and wireless interface, new energystorage technologies or self-powered energy sources are needed to drive for longer time. Since conventional energy-storage technologies based on chemicals have disadvantages such as finite life-time, instability and large scale, these disadvantages are blocking a miniaturization of the device. Moreover, the conventional self-powered source has also generated a little power in comparison with a scale. With the equipment of a self-power generator or an additional electricpower compensator on a fundamental battery, it is necessary to extend the life-time of the devices [1-4]. This study is a development of a membrane material to apply to the membranetype micro-generator for portable electronic devices which are related to a human voice. In all of energy harvesting technologies, we have focused on human voice to extend the battery time of portable electronic devices. A frequency of human voice is 80~4k Hz. However, the bandwidth of 90~400 Hz is used to speak ordinarily. Then, high conversion efficiency can be expected by realizing a resonant frequency as low as 100 Hz for receiving parts of the devices. Since a human voice has irregular frequency and energy as an acoustic wave, we have conceived a membrane structure formed by piezoelectric material which has low resonant frequency and low density material. For this reason, we have studied about a micro-generator using MEMS technology and piezoelectric polymer called by P(VDF-TeFE) (Poly Vinylidene Fluoride and Tetrafluoroethylene) (supported by Daikin Co.Ltd.) which closely resembles PVDF in a molecular structure [5-7]. As summarized in Table 1, for average mechanical parameters of P(VDF-TeFE) and PVDF film, a resonant frequency of PVDF film is almost double compared with that of P(VDF-TeFE) film because elastic m
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