Hydrogen Absorption and Desorption Characteristics of Proton Conductor Litium Compounds

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Hydrogen behavior in oxides is closely related to research and development of engineering materials such as fission and fusion reactor materials, high-corrosion resistance materials and fuel cell materials. There is limited information about hydrogen behavior in oxides. In the present study, Li_2O,Li_2ZrO_3 and SrCe_<0.95>Yb_<0.05>O_3 have been selected as candidates of proton conductors, and the hydrogen absorption and desorption behavior were examined. The electrical conductivities of Li_2O and Li_2ZrO_3 were measured in vacuum, oxygen and in O_2/H_2O atmospheres (P_<H20> of 0,100Pa, 400Pa and 872Pa) in the temperature range of 300-1000ﾟC by a impedance spectroscopy. The temperature dependence of conductivity multiplied by temperature (sigmaT) followed the relation sigmaT=Aexp (-E/RT). These results indicate that both samples are ionic conductors. The conductivities increased with increasing water vapor pressure in the oxygen atmosphere. The activation energies of conductivities of Li_2O and Li_2ZrO_3 were 64-68 kJ/mol and 97-101 kJ/mol, respectively. The hydrogen dissolution behavior of Li_2O and SrSrCe_<0.95>Yb_<0,05>O_3 was measured in the O_2/H_2O atmosphere by thermal desorption method. The hydrogen solubility was found to decrease with the temperatrue and to increase with the water vapor pressure. The equilibria between the atmosphere and oxides was discussed in terms of thermochemical reaction.