Optimization Of Preparation Process Of GDC Nano-powders And The Study Of It Used As Interlayer For SOFC Single Cell

In the last20years, Solid oxide fuel cells (SOFCs) achieved a lot of research results.The high working temperature of the traditional SOFC will lead to the short cell life andthe high cost. Therefore, improving the catalytic performance of the electrode andreducing the operating temperature of the cell has become the research focus. The mixedion-electronic conductor LSCF has higher catalytic activity for O2than the pureelectronic conductor LSM (the traditional cathode materials), so the cell which usedLSCF as cathode has higher discharge performance in the low temperature. But LSCFreacts with the traditional electrolyte YSZ to generate low conductivity, which will affectthe cell performance. In addition, its thermal expansion coefficient is different with YSZ,and they will be easily stratified after repeated thermal cycles. In this psper, the study ismainly around preparation of GDC interlayer which has good matching and chemicalcompatibility with electrolyte and electrode.Urea and NH4HCO3were respectively used as precipitant to prepare GDC (10mol%Gd2O3doped CeO2) nano-powders in this paper. By comparing the morphology of thetwo kinds of powders and the performance of the sintered bodies, GDC prepared byNH4HCO3as precipitant was more suitable for the preparation of the interlayer with highdensity and good oxygen ionic conductivity. The effect factors such as aging temperature,aging time, reaction temperature and washing methods on particle size and aggregateddegree of GDC were investigated, and the optimum conditions were obtained as follows:NH4HCO3as precipitant,40℃reaction temperature,80℃aging temperature,6h agingtime and ethanol-washing.Adding the sintering agen Bi2O3can effectively reduce the sintering temperature ofGDC to1280℃, therefore the reaction between GDC and YSZ when co-firing underhigh temperature could be prevented. Relative density of the sample increased with theadding of Bi2O3, and it reached the maximum density with3%Bi2O3. The GDCconductivity varied as the density change got up to0.05388S/cm.Under the same conditions (3%H2O+H2as fuel, air as oxidizing gas, at700℃), thepolarization resistance and the onmic resistance of the cell with GDC interlayer were1.13Ωcm2and0.45Ωcm2, respectively, much less than the cell without the layer. The cellperformance would be improved by addition of the barrier layer because it could avoidthe reaction between the cathode and the electrolyte, and prevent the generation of thehigh impedance material Sr2ZrO4and La2Zr2O7. The results showed that the maximumpower density of cells with and without GDC layer were0.70W/cm2and0.24W/cm2.