Dielectric permittivity and electrical conductivity of tungsten–silica nanocomposites

The electrical properties of nanocomposite materials composed of nano-sized amorphous silica particles and micron-sized tungsten grains were investigated as functions of composition and temperature. The dc conduction mechanism was identified to be the variable range hopping, obeying the general relationship of ln(σ)=A−BT−1/4. The dielectric constant and ac conductivity increase with increasing temperature. This combined increase is unique to this nanocomposite system and is attributed to the increase of charge carrier amount and high density of interfaces.