Dielectric properties of poly(vinylidene fluoride)/CaCu3Ti4O12 nanocrystal composite thick films

Abstract

Recently, the high dielectric permittivity composite materials have been considered to be potential candidates for integration into electronic devices. Owing to the continuous development towards the miniaturization of electronics, newer dielectric materials were sought which would enable to achieve high energy density for capacitor applications. Ceramics possessing very high dielectric permittivity are being used as voltage capacitors due to their high breakdown voltages. However, they are brittle, suffer from poor mechanical strength and hence cannot be exposed to high fields. Polymer films such as polyester, polycarbonate, polypropylene, polystyrene and polyethylenesulphide are being used in the fabrication of low leakage capacitors. Though polymers possess relatively low dielectric permittivity, they can withstand high fields, are flexible and easy to process. By combining the advantages of both, one can fabricate new hybrid materials with high dielectric permittivity, and high breakdown voltages to achieve high volume efficiency and energy storage density for applications in capacitors as electric energy storage devices In order to enhance the dielectric permittivity of polymers, ceramic powders such as Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 (PMNT), Pb(Zr,Ti)O 3 (PZT), BaTiO 3 (BT) Recently, CaCu 3 Ti 4 O 12 (CCTO) ceramic which has centrosymmetric bcc structure (space group Im3, lattice parameter a 0.7391 nm, and Z = 2), has been used as a filler and studied to explore the possibility of obtaining high dielectric permittivity composites for potential capacitor applications It was reported that, the dielectric permittivity as high as 740 at 1 kHz was achieved for a composition of fixed concentration: 50 vol% CCTO and 50 vol% . The dielectric permittivity increases as the CCTO content increases