Solid polymer electrolyte PEO9 Mg(ClO4)(2) incorporating 10 wt.% nano-porous Al2O3 filler grains has been prepared by the solvent casting technique using acetonitrile as the common solvent. Al2O3 powder (activated acidic, Aldrich) with gain size 104 mu m and pore size 5.8 ran were incorporated as an inert filler. Electrolyte films have been characterized by differential scanning calorimetry, complex impedance and dc polarization measurements. The nano-composite electrolyte as well as the filler-free electrolyte appear to be predominantly anionic conductors with ClO4(-) ions being the migrating species. The presence of the alumina filler has enhanced the ionic conductivity significantly. The conductivity enhancement has been attributed to Lewis acid-base type interactions between H groups at the filler grain surface and the ClO4(-) ions. Transient H-bonding through these interactions is expected to provide additional hopping sites and favourable conducting pathways for migrating ionic species. (c) 2005 Elsevier B.V. All rights reserved.