Electrical Conductivity in LDPE Containing Nanosized Barium Strontium Titanate Particles

DC conductivity and AC impedance measurements were made in vacuum on samples of low density polyethylene to which nano-sized BaSrTiO₃ particles (60/40 barium/strontium ratio) and a dispersant had been added. The samples were 150-200 mum thick. The temperature range was 30-70degC. The vacuum dc conductivity in samples containing the dispersant and 10% w/w nanosized BaSrTiO₃ was roughly one order of magnitude lower than that in a sample containing dispersant only. However, the vacuum dc conductivity did not follow an Arrhenius dependence on temperature closely in any of the samples, the activation energy decreasing from approximately 1.5 eV at 30degC to approximately 0.9 eV at 70degC. Addition of nanoparticles also reduced the conductivity at 30degC in air, but only by a factor of 2-3. The AC impedance measurements were made in the frequency range 10 mHz - 100 kHz. Addition of 10% w/w nanoparticles increased epsiv´ from roughly 2.34 to around 2.58 at 30degC, in air and in vacuum. However, the corresponding increase in samples containing 0.4% w/w of the dispersant alone was from 2.34 to 2.49. In vacuum at 70degC the dissipation factor (tan delta) in samples without dispersant or nanoparticles increased rapidly from approximately 0.001 at 1 Hz to 0.05 at 10 mHz. The corresponding increase in samples with dispersant and nanoparticles was much smaller. This increase was not observed at 30degC, in vacuum or in air.