Polymer electrolytes comprising a blend of poly(vinyl alcohol) (PVA) and poly(methyl methacrylate) (PMMA) with different concentrations of LiBF4 are prepared using a solvent-casting technique. The structure and complexation of the electrolytes are studied by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The ionic conductivities of the electrolytes are measured in the temperature range 302-373 K. The maximum conductivity (1.2886 x 10(-3) S cm(-1)) is obtained for a polymer complex with 8 wt.% LiBF4. The thermal stability of this electrolyte is examined by thermogravimetric/differential thermal analysis (TG/DTA). (C) 2003 Elsevier B.V. All rights reserved.