The perovskite BaCe(0.9 (-) x)ZrxY0.1O(3 (-) (delta)) has been prepared by solid state. reaction at 1400 degrees C and conventional sintering at 1700 degrees C. Water uptake experiments performed between 400 and 600 degrees C, at a water vapour pressure of 0.02 atm, provide data on the concentration of protons incorporated in the sample. The direct current conductivity has been measured as a function of oxygen partial pressure, at a water vapour partial pressure of 0.015 atm. The total conductivity has been resolved into a p-type and an ionic component using a fitting procedure appropriate to the assumed defect model. An estimation of the protonic component was made by assuming a conductivity isotope effect between 1.4 and 1.8. The total conductivity, obtained using impedance spectroscopy has been measured as a function of temperature in the water and heavy water exchanged states. The activation energy has been found to be 0.56 eV to 0.59 eV in the water exchanged state with values 0.03 to 0.04 eV higher in the heavy water exchanged state. Impedance spectra measured at 200 degrees C showed a reduction in grain boundary resistivity with increasing cerium content. The stability of the compounds to carbon dioxide has been studied by thermogravimetry. (C) 2009 Elsevier B.V. All rights reserved.