Journal of Research Updates in Polymer Science, 2014, 3, 157-169 157 E-ISSN: 1929-5995/14 © 2014 Lifescience Global Copper Ion Doped Mullite Composite in Poly (vinylidene Fluoride) Matrix: Effect on Microstructure, Phase Behavior and Electrical Properties Kumaresh Halder 1 , Biplab Kumar Paul 1 , Biswajoy Bagchi 2 , Alakananda Bhattacharya 1 and Sukhen Das 1,* 1 Department of Physics, Jadavpur University, Kolkata- 700 032, India 2 Fuel Cell and Battery Division, Central Glass and Ceramic Research Institute, Kolkata 700032, India Abstract: Highly crystallized copper ion doped mullite composites have been synthesized at 1100°C and 1400°C via sol- gel technique with five different strengths of copper ion and was incorporated in poly-vinylidene fluoride (PVDF) to make doped mullite composite/polymer films. We have studied the effects of this dopant on microstructure, phase transformation, and electrical properties of the polymer films over a wide range of frequency from 1.0 KHz to 2.0 MHz. Characterizations were done by various analytical tools at room temperature. Prominent mullite phases were observed from XRD, FTIR spectroscopy and FESEM characterization of composite polymer. The concentration of the dopant and the sintering temperature were found to be the two basic factors which affect the phase transition of the polymer. The composite film showed maximum dielectric constant of 19.96 at 1 KHz for 1.2M concentration of copper ion doped mullite sintered at 1400°C, compared to 3.09 for the pure polymer. Furthermore, both dielectric constant and electrical conductivity of the composite were found to be highly frequency and temperature dependent. After doping, the A.C. conductivity of the composite was found to increase with increasing temperature following Jonscher’s power law and the electrical resistivity reduced too. Moreover, the results revealed that the phase behaviors and micro structural changes of the copper ion doped mullite composite/polymer film affected its electrical properties with possible impact on its applications. Keywords: Polymer, Mullite, Sol–gel technique, XRD, FTIR, Dielectric properties, FESEM. INTRODUCTION Polymorphism is an essential characteristic of Poly vinylidene fluoride (PVDF). PVDF is a semi-crystalline polymer having four crystal polymorphs referred to as , ,  and  phases [1, 2]. Conventional melt and solution processing usually result in  phase which has trans-gauche-trans-gauche (TGTG) chain conformation [3, 4].  phase has all trans (TTTT) zigzag chain conformation; formation of this phase in PVDF is dependent on stretching of the film as well as the preparation temperature [5, 6].  phase has TTTGTTTG' chain conformation which can be achieved by either casting from dimethyl sulfoxide (DMSO) or dimethylformamide (DMF) solution regardless of preparation temperature [7]. High electric field, high pressure and annealing temperatures are also responsible for producing  phase [8-11]. The main advantage of polymer matrix over ceramic materials is its mechanical quality and it can also be synthesized easily. It has been observed that pure polymer matrix possesses large breakdown strength, good flexibility and great mechanical strength; it is easy *Address correspondence to this author at the Department of Physics, Jadavpur University, Kolkata- 700 032, India; Tel: +91 9433091337; E-mail: sukhenjudas@gmail.com to process but has a very low dielectric constant [12- 14]. On the other hand, ceramic composites generally suffer from brittleness which can be reduced to a commendable extent by integrating ceramic composites into the polymer matrix. Micro scale ceramics of high dielectric constant are used as fillers in polymer to increase its dielectric constant [15-17]. For such composites, filler loadings should be high enough for attainment of that range of dielectric constant that is high enough for industrial applications purposes. Though the electrical resistivity of polymer is quite high which makes it suitable to be categorized as an insulator still its electrical properties could be enhanced by incorporation of fillers in polymeric matrix as these fillers interact with the polymer chains. Thus these composites have the ability to exhibit new properties that single phase materials do not possess [18]. Thus, novel composites with comparatively high capacitance, high-energy storage density, and small volume can be prepared, which are known to be very useful materials for varieties of applications in electronics such as, transducers, hydrophones, piezo- sensors, high-charge storage capacitors [19], etc. Roy et al. synthesized highly crystallized mullite composite at 1000 o C and 1300 o C via sol gel technique For Author's Personal Use