Effect Of Sintering Aids On The Microstructure And Ionic Conductivity Of CeO₂/LSGM Electrolytes

The composite electrolyte CeO₂-La Ga O3 has been widely regarded as promising.While CeO₂ has a cubic fluorite-type structure,strontium magnesium-doped La Ga O3?LSGM?has a perovskite structure.Two-phase interfacial lattice mismatch leads to an abundance of micro-structural defects.The ionic conductivities of composite electrolytes are much higher than those of the single-phase CeO₂ or La GaO3.However,one of the main issues associated with the composite electrolyte is related to its relatively poor densification behavior,which requires high temperatures for sintering.The principal approach proposed to reduce the sintering temperature is to use sintering aids,transition metal oxide?TMO?which increases the sintering and conductivities.Ce_0.8Nd_0.2O_1.9?NDC?and La_0.8Sr_0.2Ga_0.8Mg_0.2O3-??LSGM?electrolytes were prepared using a sol-gel method.NDC-LSGM composite electrolytes were subsequently prepared by adding precalcined LSGM powders to NDC sols.And ionic transport properties of 1mol% transition metal oxide?MoO3?FeO1.5?CoO?doped NDC nanomaterials have been studied by correlating the electrical and sintering.We finally investigated the effect of the phase composition,microstructure and electrochemical properties of the composite system NDC-LSGM was investigated by adding CoO as a sintering aid.?1?The La_1-xSrxGa1-yMgyO3-? electrolyte?LSGM9191?LSGM9182?LSGM8291?LSGM8282?with different doping amounts of Sr and Mg was prepared by sol-gel method.The effects of different doping amounts of Sr and Mg on the structure and properties of La_1-xSrxGa1-yMgyO3-? were studied.The addition of Sr-and Mg-doping amounts has an effect on the oxygen vacancy.The more the doping amount is,the more oxygen vacancies are,and can improve the oxygen ion transport.Therefore,the electrical conductivity of La_0.8Sr_0.2Ga_0.8Mg_0.2 O₂.8?LSGM8282?turned out to be the highest among those of the four LSGMs.?2?On the basis of single-phase electrolyte NDC and LSGM,composite electrolytes with different mass ratios?NDC to LSGM is 95: 05,90: 10 and 85:15,respectively?were prepared.The composite electrolyte NDC-LSGM showed cubic fluorite structure,and the difference of the composite ratio did not affect its structure.The addition of LSGM can promote grain growth and improve grain boundary conductivity.The grain boundary conductivity and total conductivity of NDC-LSGM9505 samples were the highest.?3?The addition of 1 mol% of different sintering auxiliaries?MoO3,FeO1.5,CoO?in single phase NDC did not change its cubic fluorite structure.The addition of sintering aids can increase relative density and improve conductivity.CoO is demonstrated to be an effective sintering aid.?4?Five electrolytes based on Ce_0.8Nd_0.2O_1.9 with or without CoO were synthesized via a sol-gel process.The cubic fluorite structure is unchanged by the addition of CoO or LSGM to NDC.As a sintering aid,CoO can further promote grain growth and increase relative density?>95%?of the NDC-LSGM composite electrolyte.And Co element may also be slightly soluble in the lattice.Although sintering property of the NDC-LSGM-Co sample is significantly improved,the grain boundary conductivity is no further improved due to the presence of trace amounts of impurity phases in the grain boundaries.