Preparation Of Lanthanum Doped Strontium Titanate And Itsapplication For SOFC Interconnect

Solid oxide fuel cell (SOFC) is a kind of new energy technology. Now the highcost is blocking its commercialization, of which the cost of preparing interconnectoccupies half and more. It plays an important roles for SOFC’s commercialization tooptimize the performance and preparation process of interconnect.At present, there are two kinds of SOFC interconnect materials normally used,heat-resistant alloy and LaCrO3based ceramic material. Both of them have their ownadvantages and disadvantages. To overcome their disadvantages, this paper mainlydecide to study the possibility of applying lanthanum doped strontium titanate (LST)as SOFC interconnect.LaxSr1-xTiO3（x=0.1,0.2,0.3,0.4,0.5）were prepared by solid reaction methodand sol-gel method. From the samples’ XRD patterns and the relative density ofsamples sintered in reduction environment (graphite-buried sintering method), it isfound that when x is over0.3, the XRD shows impurity and the samples are hard tobeen sintered to dense. As LST is n-type semiconductor, its conductivity will reachthe maximum value with the increase of La doping amount.So the La0.3Sr0.7TiO3（referred as LST hereafter）sample is the most suitable to be used in LST-LSMdouble layer interconnect.Sintered through graphite-buried method, the relative density of LST sample isover94%, the conductivity is about10S cm-1and6S cm-1tested in H2and N2atmosphere respectively. Sintered in air, the relative density of LST is over94%, theconductivity is under2S cm-1tested in H2. Sintered in air, the relative density ofLSM is over94%, the conductivity is above140S cm-1tested in air. The averagethermal expansion coefficient of LST and LSM is13.10×10-6K-1and12.96×10-6K-1respectively, which is close to YSZ material, ensuring their thermal matching. Fromthe chemical compatibility study, it is foud that LST and LSM won’t react at1400℃.From co-sintering situations of NiO/YSZ and LST under different temperatures, theNiO/YSZ anode and LST-LSM three layers can be well sintered together at1350℃,which means the anode and interconnect can be prepared with cheap cost. LSTmembrane has been prepared through slurry coating method and dip-molding method,of which the thickness is67.13μ m and28.39μ m, respectively. The AC impedanceof LST and Ni/YSZ anode is about0.25Ω cm2at850℃, which is very close to thetheoretical requirement.Of cause, it also needs further optimization and improvement. Through the study on preparation of LST, co-sintering situation, of which withanode and the characterization of related properties, it is found that LST has thepotential to be used as high temperature tubular SOFC’s interconnect.