Water vapor solubility and electrochemical characterization of the high temperature proton conductor BaZr0.9Y0.1O2.95

Abstract BaZr 0.9 Y 0.1 O 2.95 prepared at very high sintering temperatures was evaluated as to whether it displayed the high water vapor solubility claimed in recent work. A maximum solubility of 0.083 was determined which is close to the theoretically possible value. Thermogravimetry resulted in the following parameters for the solution process: Δ H o =(−0.77±0.03) eV, Δ S o =(−0.9±0.1)×10 −3 eV/K. Electron microscopy showed a bimodal size distribution of the grains. Density measurement provided evidence for the vacancies in the O-sublattice in the dry state.The relevant transport numbers were determined electrochemically. Under oxidizing conditions, hole conduction suppresses the proton transport number. Under reducing conditions, BaZr 0.9 Y 0.1 O 2.95 is a near perfect proton conductor. Oxygen ion conduction was not found to be important. The use of BaZr 0.9 Y 0.1 O 2.95 under reducing conditions allows the injection of hydrogen into inert gas streams as shown with a PEM fuel cell. DC conductivities are also presented providing a rationale for the electrochemical cell measurements.