Conductivity and space charge 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 o...

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Bibliographic Details
Published in:IEEE transactions on dielectrics and electrical insulation 2008-02, Vol.15 (1), p.118-126
Main Authors: Fleming, R.J., Ammala, A., Lang, S.B., Casey, P.S.
Format: Article
Language:English
Subjects:
Conductivity
Density
Direct current
Dispersants
Dispersion
Frequency
Impedance measurement
Nanomaterials
Nanoparticles
Nanostructure
Polyethylene
Polyethylenes
Space charge
Temperature dependence
Temperature distribution
Zinc oxide
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Summary: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 had very little effect on the dc conductivity. The ac 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 samples with nanoparticles was increased relative to that of samples containing dispersant only, at all temperatures, but the corresponding values in samples with microparticles were unchanged, within experimental error. Space charge profiles were obtained using the laser-intensity-modulation-method (LIMM). Space charge densities of order 300 Cm -3 were measured in the bulk near the electrodes, several hours after poling at field strengths around 30 kV/mm.
ISSN:1070-9878
1558-4135
DOI:10.1109/T-DEI.2008.4446742