Studies on synthesis of mixed ion conducting ceramics and their applications

合成了BaCeO_3基钙钛矿型氧化物固溶体，并研究了其高温离子导电性。在燃料电池(H2/Air)条件下，用三价阳离子部分取代BaCeO_3中的Ce，得到的氧化物陶瓷是质子和氧化物离子的混合离子导体。研究了电导率随掺杂阳离子半径r的变化。结果表明，燃料电池的最大电导率出现在r=0.90-0.95A范围内，随着离子半径的增大，氧离子电导率对总离子电导率的贡献越来越大。当BaCeO_3掺杂二价阳离子时，其质子电导率和氧化物离子电导率均有所降低。通过程序升温水蒸气脱附实验和氢同位素的电化学示踪实验，阐明二价阳离子掺杂氧化物的质子电导率较低是由于其质子含量较少，与三价掺杂样品相比，其迁移率较低。实验证明，该混合离子导体可用于乙烷制乙烯的电化学膜反应器、甲烷制C2烃的化学反应器和同时产生化学产品和电力的燃料电池。

Perovskite-type oxide solid solutions based on BaCeO_3 were synthesized and their ceramics were studied with respect to their ionic conduction at elevated temperatures. Partial substitution of trivalent cations for Ce in BaCeO_3 made the resultant oxide ceramic a mixed ionic conductor of protons and oxide ions under fuel cell condition (H_2/Air). Change in conductivity with ionic radius r of dopant cation was investigated. It was found that the maximum conductivity lay on about r = 0.90-0.95A and that the contribution of oxide ion conduction to the total ionic conductivity under fuel cell condition became marked as the ionic radius grew larger. When BaCeO_3 is doped with divalent cation, both the protonic and oxide ionic conductivities were observed to decrease. Using a temperature programd water vapor desorption experiment and an electrochemical tracer experiment of hydrogen isotope, it could be clarified that low protonic conductivity of the oxide doped with divalent cation was ascribed to small content of proton and its low mobility compared to those in trivalent doped specimens.These mixed ionic conductors were verified experimentally to be applied to an electrochemical membrane reactor for ethylene production form ethane, a chemical reactor for C_2-hydrocarbon production from methane and a fuel cell for chemical cogeneration which could produce both chemical products and electric power.