Composite membranes composed of sulfonated poly(ether ether ketone) (sPEEK) and co-precipitate of zirconium oxide and phosphomolibdic acid (ZPMA) were prepared. Inorganic ZPMA was synthesized by hydrolysis of ZrO(2)Cl(2) in the presence of phosphomolibdic acid (PMA), and its structure was examined by FTIR and XRD. While the proton conductivity of sPEEK/ZPMA composite membranes was much higher than that of pristine sPEEK membrane due to high conducting property of phosphomolibdic acid, the methanol permeability was still very low and comparable to that of pristine one. As the composite membrane had much lower water uptake than the pure sPEEK membrane, it was dimensionally stable in hot water even above 80 degrees C. The ionic cluster size and morphology of composite membranes were analyzed by SAXs and SEM, respectively. (C) 2011 Elsevier B.V. All rights reserved.