Study On Preparation And Properties Of Mixed Proton-Electron Conductor Membranes With Dual Phase For Hydrogen Permeation

The dual-phase mixed proton-electron conductors BaCe_0.8Y_0.2O₃/Y_0.09Sr_0.91TiO₃,BaCe_0.8Y_0.2O₃/Ce_0.8Y_0.2O₂, BaCe_0.8Y_0.2O₃/LaCo_0.9Ni_0.1O₃are synthesized by the solid state reactionmethod. The phase composition, microstructure and electrical conducting property of samples arecharacterized by XRD, SEM and EIS, respectively. The chemical stability of specimens against H₂,H₂O and CO₂is also tested. In addition, the effects of hydrogen concentration and temperature onhydrogen permeation properties are investigated. The results show that:The sintering temperature and doping ratio have a great effect on the phase composition andmicrostructure In a certain sintering temperature, the three kinds of the mixed conductor are formed of adual phase structure; there is no impurity phase generation. The grain size and the density of samplesincrease with increasing sintering temperature. As the second phase proportion of the mixed conductorsBaCe_0.8Y_0.2O₃/LaCo_0.9Ni_0.1O₃increase, crystal becomes more and more clear and the number of grainboundaries of the unit size reduces significantly.The stability tests in the H₂and H₂O atmospheres are conducted to determine the stability of thethree kinds of the mixed conductor; the diffraction peak intensity, peak shape and peak position hardlychange. In the CO₂atmospheres, the power samples decompose into BaCO₃and CeO₂.The sintering temperature, doping ratio and test atmosphere have an effect on the electricalproperty. In a certain sintering temperature, the electrical conductivity ofBaCe_0.8Y_0.2O₃/Y_0.09Sr_0.91TiO₃samples in4%H₂/Ar increases with increasing proportion of the electronconducting phase. The sample of BaCe_0.8Y_0.2O₃/Y_0.09Sr_0.91TiO₃=5/5sintered at1400℃has thehighest conductivity. The mixed conductors BaCe_0.8Y_0.2O₃/Ce_0.8Y_0.2O₂have different conductionmechanisms in different atmospheres. BaCe_0.8Y_0.2O₃/Ce_0.8Y_0.2O₂=3/7sintered at1550℃has thehighest conductivity in4%H₂/Ar at800℃. The mixed conductors BaCe_0.8Y_0.2O₃/LaCo_0.9Ni_0.1O₃sintered at1200℃with different ratios show different conduction mechanisms in differentatmospheres. The samples which are tested in H₂have the highest conductivity in the low temperaturesection. Electronic conductivity has become the main conductive mechanism with increasingtemperature and the samples which are tested in air have the highest conductivity.The hydrogen permeation flux increases with increasing test temperature and hydrogenconcentration. Hydrogen permeation flux of BaCe_0.8Y_0.2O₃/Ce_0.8Y_0.2O₂=3/7（1.75mm） reachs up2.4997mL·min^-1·cm^-2in40%H₂/N₂at850℃.