Effect of interparticle distance and interfacial area on the properties of insulator-conductor composites

The influence of conducting phase characteristics on dielectric properties of insulator-conductor composites was demonstrated by studying composites of polytetrafluoroethylene and different volume fractions of La0.5Sr0.5CoO3-y (LSCO). LSCO was prepared as coarse grained powder by solid state reaction and as fine powder by citrate gel method. The composites with fine powder of LSCO showed a rapid increase in dielectric constant and conductivity at 30%, while the corresponding value for coarse powder was 50%. The percolative behavior was found when the interparticle distance reduced to similar to 250 nm in both cases. The permittivity and conductivity of the composites were found to increase with the interfacial area. (c) 2007 American Institute of Physics.