Dielectric behavior of Ag/BaTiO3/epoxy nanocomposites

LEANDRO RAMAJO; MIRIAM CASTRO; MARIA MARTA REBOREDO

Rio de Janeiro, Brasil

Congreso; International Conference on Science and Technology of Composite Materials; 2007

Polymer-ceramic materials have arisen much attention mainly for uses in microelectronic packaging, due to their good performance and low cost, size and weight. In this way, BaTiO3 has demonstrated to have good performance as filler because of its high dielectric permittivity. Nevertheless, there is a new generation of conductive nanofiller which can be incorporated to BaTiO3 / epoxy composites in order to obtain better material performance. The dielectric properties of the composites with metallic filler are attributed to the formation of infinite number of tiny capacitors with many conducting particles separated by thin insulating layers. Thus, a heterogeneous system of this kind can result in a capacitor with excellent characteristics for charge storage. In this work, BaTiO3 epoxy composites were made incorporating 1% wt of functionalized nanosilver. These nanoparticles were obtained through AgNO3 chemical reduction in ethanol and triethylenetetramine (D.E.H 24) was used to stabilize and functionalize the metal in a 1:10 relation Ag / D.E.H 24. The composite material were prepared mixing epoxy functionalized Ag in a 17.5 phr relation and BaTiO3 was added in 35 to 45%vol. Each system was mixed with using an ultrasonic mixer during 4 minutes and composites were prepared by the dipping technique. Dielectric measurements were performed from 25 Hz to 1 MHz and 20 ºC to 120 ºC. It was found that the Ag – BaTiO3 – epoxy composites had higher permittivity than classic BaTiO3 epoxy composites. Relaxation processes were influenced by the epoxy resin near the Tg, while metallic and ceramic content modified the real permittivity values. Interfacial polarisation processes known as Maxwell-Wagner-Sillar were generated by metallic particles. They produced an accumulation of charges on the interface that helped to displace the relaxation peaks to higher frequencies.