Dielectric Properties of CaCu3Ti4O12-P(VDF-TrFE) Composite
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0949-C05-07
Dielectric Properties of CaCu3Ti4O12-P(VDF-TrFE) Composite Xiaobing Shan, Xin Yang, Kewei Zhang, and Zhongyang Cheng Materials Research and Education Center, Auburn University, Auburn, AL, 36849
ABSTRACT By using conventional solution casting method, a flexible ceramic [CaCu3Ti4O12 (CCTO)]Polymer [P(VDF-TrFE)] composite has been fabricated. The CCTO ceramic powders with a relative uniform size were prepared by traditional powder processing method. The dielectric properties of these films with different CCTO fractions were determined. The process was optimized to achieve high dielectric constant. A dielectric constant about 510 at room temperature and 1240 at 95 ˚C at 1 kHz for 6 layer hot compression was obtained. INTRODUCTION Polymer materials like Poly(vinylidene fluoride) (PVDF), Poly(vinylidene fluoride)-coTrifluorethylene [P(VDF-TrFE)], with good piezoelectric and pyroelectric properties have been widely used in many applications, such as charge-storage, actuators, and artificial muscles[1,2,3,4]. As dielectric materials, it is desirable to achieve high dielectric constant. For polymer materials, it has high flexibility and high dielectric strength, however its dielectric constant is very low. Therefore, there is a great need to develop a new polymer composite which can both have high dielectric constant and high flexibility. In order to develop the polymer composite, the ferroelectric ceramics have been used as filler and the properties of composite have been optimized. However, the composite shows strong coupling effect which will influence the reliability of the composite. Besides the ferroelectric ceramics, metal oligomer such as CuPc, PANI and metal particle such as Ni have been applied to make polymer composite with high dielectric constant, however because it is related with percolative phenomenon, the processing is difficult to control [5,6,7]. Recently, the high/giant dielectric constant about ~10000 for ceramic and ~100000 for single crystal with a weak temperature dependence over a broad temperature range was obtained in CaCu3Ti4O12 (CCTO) without piezoelectric effect [8,9,10]. In the experiment, a novel ceramic composite with CCTO as filler and poly(vinylidene fluoride–trifluoroethylene) [P(VDF-TrFE] 55/45 mol% copolymer as matrix has been prepared. Composites with different CCTO volume fraction have been studied. Influences of CCTO particle under different experiment routes to final result have been studied. In order to improve the wettability, hot compression process has been used to eliminate the porosity and increase the density. After optimizing the CCTO particle and the hot compression process (HC), a dielectric constant about 510 at room temperature and 1240 at 95 ˚C at 1 kHz with loss around 0.2 for 6 layer hot compression was obtained.
EXPERIMENTAL Synthesis of CaCu3Ti4O12 (CCTO) The ceramics have been prepared using the conventional powder processing method. The raw oxides and carbonate are weighted according to the stoichiometric ratio and then mixed in a polyethylene bott
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