Investigation On Preparation And Properties Of BaCeO₃-based Proton Conductors

Proton conductors BaCe0.7Nb0.1Y0.2O3-δin different calcination temperature, proton conductor BaCe0.8-xNbxGd0.2O3-δ(0≤x≤0.45) doped with different concentrations and proton conductor BaCe0.7M0.1Y0.2O3-δ(M=Zr, Ti, Zn, Sn, Nb) doped with different elements were prepared by high-temperature solid-state reaction method. Through using the technology of XRD, SEM and EIS, phase structure, micro-morphology and electrical conductivity of the materials were studied respectively. The stability in the atmosphere containing water vapor, H2 and CO2 was also studied. The limiting current hydrogen sensors were prepared with the dense diffusion layer of mixed conductors BaCe0.7Zn0.1Y0.2O3-δ: Ce0.8Y0.2O2=5:5(volume ratio, sensor 1) and 6:4(sensor 2) and with the solid electrolyte of BaCe0.7Zn0.1Y0.2O3-δ, then the hydrogen-sensitive properties of it were studied.The results showed that all of proton conductors formed perovskite structure. The densification of sintered samples of BaCe0.7Nb0.1Y0.2O3-δincreased with the calcination temperature of powders raised. This conclusion was also consistent with thermodynamic calculations. At 700℃, the stability of all the sintered samples was good in the atmosphere containing water vapor and H2, but it was poor in the atmosphere of pure CO2. In wet 4000ppmH2/Ar atmosphere, the conductivity of sintered samples of different calcination temperature was or less. The optimal calcination temperature of proton conductor BaCe0.7Nb0.1Y0.2O3-δwas at 1300℃.The densification of sintered samples of BaCe0.8-xNbxGd0.2O3-δ(0≤x≤0.45) increased with the value of x increased. At 700℃, the stability of all proton conductors was good in the atmosphere containing water vapor, and the stability increased with the value of x increased in pure CO2. But the stability of all proton conductors at 800℃was better than at 700℃in the atmosphere of pure CO2. This conclusion was also consistent with thermodynamic calculations. In wet 4000ppmH2/Ar atmosphere, the conductivity decreased with the value of x increased. When x = 0.1, the property of the sintered samples was best.The densification of sintered samples BaCe0.7M0.1Y0.2O3-δ(M=Zr, Ti, Zn, Sn, Nb) from good to poor was followed by Zn, Nb, Ti, Sn, Zr. At 700℃, the stability of all the sintered samples was poor in the atmosphere of pure CO2, but it was good in the atmosphere containing water vapor and H2. In wet 4000ppmH2/Ar atmosphere, the conductivity of sintered samples of Ti-doped and Zr-doped was the minimum and maximum respectively.At 700℃, there was a good linear relationship between response current at 0.4V and hydrogen concentration, hydrogen concentration was in the range of 50~999ppm, of sensor 1 and sensor 2. The correlation coefficient was 0.998 and 0.995, and the sensitivity was 3.137 and 2.349μA ? ppm-1 at 700℃, respectively.