The preparation and ionic conductivity of a new class of ionic conducting composite polymer electrolytes (CPEs), poly(methoxyethoxyethoxy)phosphazene (MEEP)/lithium perchlorate (LiClO4)/alpha-Al2O3, formed by dispersing alpha-Al2O3 particles into MEEP/lithium perchlorate electrolytes are reported and discussed. The addition of alpha-Al2O3 leads to an enhancement of the conductivity in the composite polymer electrolytes prepared. The best conductivity obtained from the composite polymer electrolyte with 2.5 wt.% alpha-Al2O3 and 0.2 LiClO4 per polyphosphazene repeat unit is close to 10(-4) S cm(-1) at room temperature, which is the highest reported for the MEEP-based electrolytes. From the results of FTIR spectroscopy, DSC measurement, cation transport number and the temperature dependence of conductivity, an ion transport mechanism in the composite polymer electrolytes is proposed. (C) 2003 Elsevier Science B.V. All rights reserved.