Composite polymer electrolytes comprising of a poly ethylene oxide (PEO)-NaClO4 complex dispersed with Na2SiO3 are described. The results of the studies based on optical microscopy, X-ray diffraction, differential scanning calorimetry, a.c. impedance analysis and mechanical testing are presented and discussed. An electrical conductivity of 1.02 x 10(-3) S cm(-1) at 100 degrees C was achieved with a dispersion of 1 wt% of Na2SiO3. A substantial enhancement in the mechanical proper:ies of the composite films was observed at the cost of a slight decrease in the conductivity. The temperature dependence of conductivity follows an Arrhenius type thermally activated process below and above the melting temperature of PEO. (C) 1998 Elsevier Science Ltd. All rights reserved.