The proton conducting electrolyte cerium pyrophosphate was synthesized by digesting cerium oxide with 85% H3PO4. The crystal structure and phase stability of the material were analyzed by X-ray diffraction and thermogravimetric analysis/differential thermal analysis (TGA/DTA), and the microstructure was analyzed by scanning electron microscopy (SEM). The electric conductivity behavior of CeP2O7 sintered pellets was analyzed by electrochemical impedance spectroscopy (EIS) and modulus spectroscopy. The activation energies for migration (E-omega) and dc conduction (E-sigma) calculations indicates that the charge carriers responsible for conductivity and relaxation are same and the concentration of charge carries is independent of temperature. The variation of conductivity with temperature was studied in dry and humid atmosphere for the possible application as electrolyte in proton conducting ceramic electrolyte fuel cells (PCFCs) in the temperature range of 100-220 degrees C, which showed that the conductivity of CeP2O7 was mainly due to the incorporation of water and the maximum conductivity was found to be 2.1 x 10(-4) S cm(-1) at 175 degrees C and P-H2O = 0.06 atm. The presence of water in CeP2O7 matrix increases the number of jump sites and facilitates the hopping of protons, leading to an increase in the conductivity. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.055212jes] All rights reserved.