Comparative study of dielectric properties of polymer based composites containing barium titanate modified with different kinds of nanotubes

The effect of modification of barium titanate (BaTiO$_3$) submicron particles by the deposition of different kinds of nanotubes (carbon single- and multiwall, as well as comprising potassium polititanate K$_2$Ti$_6$O$_{13}$) upon dielectric properties of composites obtained by incorporation of thus modified BaTiO$_3$ into cyanoethyl ester of polyvinyl alcohol as a polymer binder is studied. The introduction of all the applied nanotubes in relatively small amounts (below 0.1 vol.%) provides a growth of the dielectric permittivity of the composites due to the improvement of their structural uniformity, while the addition of higher amounts of carbon nanotubes results in percolation with an abrupt increase of electrical conductivity due to the formation of conducting pathways comprising networks of interconnected nanotubes. The permittivity of the studied composites is found to grow with an increase of fractal dimension and decrease of lacunarity characterizing a non-uniformity of filler distribution in the polymer binder.