Electrical conductivity in LDPE containing nano- and micro-sized ZnO particles

Dc conductivity and ac impedance measurements were made in air and in vacuum on samples of low density polyethylene to which nano-sized and micro-sized ZnO particles and a dispersant had been added. The samples were 150-200 mum thick. The temperature range was 30-70degC. The temperature dependence of the vacuum dc conductivity in samples containing the dispersant and 10% w/w nanosized ZnO followed an Arrhenius relationship closely, the conductivity being 1-2 orders of magnitude lower than that of a sample containing dispersant only. The addition of 10% w/w microsized ZnO also reduced the dc conductivity, but to a much lesser extent. The ac impedance measurements were made in the frequency range 10 mHz - 1 MHz. Addition of nanoparticles increased the ac conductivity at higher frequencies but decreased it at lower frequencies, the cross-over frequency increasing with increasing temperature. The real part of the relative permittivity of the nanosamples was increased relative to that of samples containing dispersant only, at all temperatures, but the values in the microsamples were equal to those in samples with dispersant only, within experimental error.