Study on dielectric properties of nano and microcomposites BaTiO3/epoxy

L. RAMAJO; R. GIMENES; M RENOREDO; M. SAGHETE; M CASTRO

Buenos Aires

Congreso; Third International Conference on Science and Technology of Composite Materials (COMAT); 2005

Dielectric properties of BaTiO3/epoxy composites and nanocomposites were characterized in order to study the influence of particle size on the dielectric behavior of composites. Nb2O5-doped BaTiO3 was chosen because of their good dielectric properties. Ceramic microparticles were obtained by powder mixture. The powder was milled in isopropilic medium using a planetary mill with ZrO2 balls for 90 min to guarantee better dispersion during the mixing. Barium titanate nanoparticles were obtained by soft chemical mixing citrates of Ti, Ba and Nb. The thermal treatment was driven at temperatures ranging from 250ºC to 700ºC during 4 hours in order to reduce the BaCO3 formation.  Epoxy was diluted using tetrahydrofuran (75% wt) to reduce matrix viscosity and to facilitate the mixing step. Particle distribution was characterized using a Bi-XDC Brookhave Instruments and lattice parameters were characterised by X-Ray Diffraction. Both, nanoparticles and microparticles, were mixed with the resin during 5 minutes in a ultra sound bath. Composite films onto glass plates were spin coated at (XRMP). Microstructures of the polished samples were examined by scanning electron microscopy (JEOL 6460LV). Dielectric measurements were performed from 25 Hz to 1 MHz and from 20 to 120 ºC using a Hewlett Packard 4284A Impedance Analyzer. It was found that the final materials had low porosity and defects and that permittivity was strongly dependent on the filler concentration. Electrical relaxation was generated by resin dominions detected in the composite and it was influenced by temperature and solvent concentration.