Study on dielectric properties of nano/microcomposites of epoxy/BaTiO3

ROXANO GIMENES; LEANDRO RAMAJO; MARIA MARTA REBOREDO; MARIA APARECIDA SAGHETE; MIRIAM CASTRO

Buenos Aires

Congreso; International Conference on Science and Technology of Composite Materials; 2005

COMAT - UNMdP

Dielectric properties of composites and nanocomposites epoxy/BaTiO3 were characterized in order to study the influence of the particles size on the dielectric properties of composites. Nb2O5-doped BaTiO3 were chosen because of their good dielectric properties. The ceramic microparticles were obtained by power 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 250ºC at 700ºC during 4 hours in order to reduce the BaCO3 formation.  Epoxy was diluted using tetrahydrofuran (75% wt) as solvent to reduce matrix viscosity and to facilitate the mixing step. Particles distribution was characterized using a Bi-XDC Brookhave Instruments and lattice parameters were characterised by X-Ray Diffraction. Nanoparticles and microparticles were mixed with the resin during 5 minutes in a ultra sound bath. Composite films onto glass plate were spin coated at (XRMP). Microstructures of the polished samples were examined by scanning electron microscopy. Dielectric measurements were performed from 25 Hz to 1 MHz and 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 dependence with the filler concentration. Nanocomposites had not too better properties than the composites made of microparticles. Electrical relaxation was generated by resin dominions detected in the composite and it was influenced by temperature and solvent concentration.