Synthesis And Characteristics Of BaCe_0.9-xZr_xM_0.1O_3-δ (M=Gd,Nd) Proton Conductors

Since Iwahara et al. first reported the proton conductivity of a perovskite type Y doped SrCeO₃ solid solution in 1981, interests in this type of materials have remained high due to the possibility of using them as solid electrolytes in electrochemical devices such as fuel cells, hydrogen separation, gas sensors, ammonia synthesis, et al.. At present rare earth doped BaCeO₃ exhibit the best proton conductivity. However, BaCeO₃ based materials will decompose in CO₂ atmosphere. BaZrO₃ based materials are more stable in CO₂ atmosphere, but their sintering temperature is very high(＞1600℃).In this thesis, an investigation on the synthesis and measurement of proton conductivity of mixed BaCeO₃ and BaZrO₃ based ceramics has been carried out. The designed solid electrolyte ceramic compositions are BaCe_0.9-xZr_xM_0.1O_3-δ (x=0.1, 0.2, 0.4; M=Gd, Nd). The solid electrolytes were synthesized by Pechini method. Dry powders were calcined at 1100℃. Pellet samples were prepared by first pressed the powders and then sintered at 1450℃. Powder samples or pellet samples were characterization by TG-DTA, XRD, SEM and AC impedance spectroscopy.The XRD results shows that perfect perovskite phases were synthesized by calcined the dried powders at 110℃. The densities of sintered ceramic pellet samples are greater than 93ï¼…of their theoretical densities by sintering at 1450℃. SEM shows the dense microstructure of the ceramic samples. AC impedance measurements reveal that the samples have good proton conduction in moist air atmosphere. Gd doped solid electrolyte BaCe_0.8Zr_0.1Gd_0.1O_3-δ has higher conductivity than that of Nd doped solid electrolyte BaCe_0.8Zr_0.1Nd_0.1O_3-δ.