The Study On Preparation And Electrical Properties Of BW-NDC/Nonstoichiometric LSGM Electrolyte

CeO₂-based and LaGaO₃-based electrolytes are the most interesting candidates for intermediate temperature solid oxide fuel cell?IT-SOFCs?because of the higher conductivity than ZrO₂-based electrolytes.However,the main limitation of the CeO₂-based and LaGaO₃-based electrolytes are the high sintering temperature and the electronic conductance in the presence of reducing atmosphere in CeO₂-based electrolytes,and the low conductivity of LaGaO₃-based electrolytes at low temperatures.In this paper,Nd₂O₃-doped CeO₂(Ce_0.8Nd_0.2O_1.9,NDC)and SrO and MgO-doped LaGaO₃(La_0.9Sr_0.1Ga_0.9Mg_0.1O_3-?,LSGM)electrolytes were prepared by sol-gel method.The effects of the addition of Bi₂WO₆?BW?on the sintering properties,interfacial effects and electrical conductivity of NDC electrolytes were investigated.Secondly,the effects of non-stoichiometric ratios of A/B-site on the microstructure,ionic conductivity,thermal expansion coefficient of LSGM electrolyte were examined and compared.The main results as show:?1?Addition of proper BW phase can decrease the sintering temperature,effectively increase the density,inhibit the electronic conductance,enhance the oxygen reduction reaction activity with the cathode,and improve the conductivity of the NDC electrolyte material.BW-NDC composite electrolyte is composed of NDC phase with cubic fluorite structure and BW phase with perovskite structure;addition of BW obviously promote grain growth and improve grain boundary conductivity due to introduce a large number of phase interfaces,multifunctional BW phase can effectively inhibit and reduce the detrimental effects of electrons conductivity,which significantly increase the ionic conductivity.The ionic conductivity of BW-NDC composite electrolyte reached 0.0126 S·cm^-1 at 600°C,which is nearly one order of magnitude higher than NDC(0.0036 S·cm^-1).A single cell prepared with a BW-NDC composite electrolyte can achieve a maximum output power density of 0.86 W·cm^-2 at 700°C,which is 45.76%higher than that of a single cell containing NDC electrolyte.?2?The beneficial effect on the interface structure and carrier density was obtained by changing the ratio of non-stoichiometric in the LSGM electrolyte,thereby improved the oxygen ion conduction performance.The perovskite structure of LSGM electrolyte remained undestroyed when non-stoichiometry changed.The LS?GM?_0.97 sample with B-defect exhibited the highest phase purity and compactness,minimum grain boundary volume fraction,decreased grain boundary resistance and total resistance,better electrical conductivity,and excellent thermal stability.The conductivity of the LS?GM?_0.97 electrolyte was 1.68×10^-2 S·cm^-1 at 800°C,which is 1.56 times higher than that of the LSGM electrolyte.The single cell prepared with LS?GM?_0.97 electrolyte can achieve a maximum output power density of 0.54 W·cm^-2 at 800°C,which is 16.7%higher than that of the single cell containing LSGM electrolyte,and the excellent stability is maintained for 120 h at least.