New composite materials were prepared using cesium hydrogen sulfate (CsHSO4) or cesium dihydrogen phosphate (CsH2PO4) and phosphosilicate gel (P2O5-SiO2 gel). In X-ray diffraction patterns of these composites, diffraction peaks due to CS2H(S0(4))(2)MPO4) and CsH5 (PO4)(2) were observed for CsHO4-(P2O5-SiO2 gel) composites and CsH2PO4-(P2O5-SiO2 gel) composites, respectively. These composites showed high. conductivities in the order of 10(-3) S cm(-1) at 150 degrees C due to melting of CS2H(SO4)(2)(PO4) or CsH5(PO4)(2) in the composites. In the cooling process, the CsHSO4-(P2O5-SiO2 gel) Composites kept relatively high conductivity to 110 degrees C where solidification of CS2H5(SO4)(2)(PO4) occurs, whereas CSH2PO4-(P2O5-SiO2 gel) Composites showed relatively high conductivity continuously to ambient temperature. (c) 2006 Elsevier B.V All rights reserved.