ZHU Xinfeng, QU Peng, LI Qinghua, LIU Xiaolin
(State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029, China)
Abstract: Finite element method was adopted to study the influences of both content (1~7vol.%) and orientation angle (θ) of B-BT on the dielectric constant of dendritic barium titanate (B-BT)/P(VDF-TrFE) composites. The breakdown strength of composites was calculated by the statistical model of the electric field distribution. The result showed that the dielectricconstant-orientation angle curves were symmetrical about θ=90°. Besides, simulated dielectric constant was close to the experimental values when B-BT||E. The breakdown strength of composites ranged from 411 to 452 kV/mm and energy storage density reached 9.5~11.5 J/ cm3 when B-BT⊥E. Electric displacement (noted D) and electric field distribution (noted E) of composites containing a single B-BT were performed. It was found that larger D and enhanced local E appeared in the tip positionof B-BT particlewhen B-BT⊥E, indicating an improvement of the dielectric constant and a reduction of the breakdown strength. While the results were opposite when B-BT⊥E. In addition, black pine dendritic barium titanate (Bp-BT) particles were designed, and the dielectric properties of Bp-BT/P (VDF-TrFE) composites were calculated. It was found that energy storage density of composites reached 10.1~12.5 J/cm3 when Bp-BT⊥E, which was better than B-BT/P(VDF-TrFE). The result indicated that Bp-BT particles may be used as an alternative inorganic material to improve the energy storage density of organic-inorganic dielectric composites.
Key words: finite element method; composites; dielectric properties; electric field analysis; electric displacement