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 ∼250nm in both cases. The permittivity and conductivity of the composites were found to increase with the interfacial area.