Preparation And Properties Of BT/PVDF Dielectric Composites

Embedded capacitor, as a circuit board component for electric storage and discharge and an effective technology, improves the electrical properties of the board with saving circuit board effective area. Currently the main problems it facing is an urgent need for high-k materials with high dielectric constant, low loss factor, high thermal stability, simple production process. Nano dielectric composite material compatible with the nanometer ceramic particles of high dielectric properties and advantages of polymer easy to processing molding, is the main candidate for embedded capacitor materials; In recent years, the preparation of embedded capacitor materials by the high dielectric ceramic particles or conductive particles dispersed in a continuous phase of three-dimensional polymer matrix received widespread attention. Therefore the study of the polymer matrix composite materials is of important practical significance.Based on this, barium titanate(BT) was selected as high dielectric fillers, carbon black as conductive component, Polyvinylidene Fluoride (PVDF) as polymer matrix, then dielectric polymer based composites was prepared by solution mixing. First, in chapter two different size of nano barium titanate powder was obtained and the influence of the reaction temperature, solvent, reaction time on morphology and structure of nanometer barium titanate were discussed. The results showed that the reaction temperature is higher when the barium titanate particles has good monodispersity; the greater the polarity the solvent is, the larger size BT particles are. On this basis, dielectric polymer composites with different sizes of BT was obtained in Chapter three, found that the dielectric constant increases first and then decreases with the increase of the size of BT. Choosing200nm BT as fillers, dielectric constant of the composite increases with the increase of the filling volume and there is an obvious frequency dispersion effect in composite materials. When the filler content is60%, the dielectric temperature spectra peak of the composites appeared at110℃. To further improve the dielectric constant of the composite material, based on the percolation theory, in the fourth chapter owe to smaller percolation threshold the carbon black was added to the BT/PVDF composites. Dielectric constant increased significantly but the loss can be controlled within the acceptable range in three-phase composites, thus which can be used as a potential application of dielectric materials.