Preparation And Performance Of Alkaline Metal-doped Rare Earth Cathode Materials

Solid oxide fuel cell with high efficiency of electricity, extensive application on fuel,whole solid-state ceramic structure, non-electrolyte loss and non-electrode corrosion andsuitable design for modular is a very promising new energy conversion system. At present,running temperature reduced to low range of500~800℃is the research and developmenthighlight.In order to reduce raw material cost and suit for industrial production, mixed RE insteadof pure lanthanide oxide is formed by nitric acid and then Ln-Sr(or Ca)-Cu-O and Ln-Sr(orCa)-Fe-O cathode materials(Ln=mixed rare earth) have been prepared by the coprecipitationmethod. In addition, Ce0.9La0.1O2-δelectrolyte materials have also been prepared by use of thesol-gel process. For the cathode materials and electrolyte materials, the influence of synthesisprocess on structures and properties of the materials have been discussed.Results show thatthe product of Ln-Sr(or Ca)-Cu-O(referred to as LnS(C)C) is the coexistence of CeO2cubicfluorite and perovskite phase. when2θ in20~30°range, doping Sr2+makes LnSC formrelatively complete perovskite diffraction peak; when2θ in30~45°range, doping Ca2+makesLnCC perovskite diffraction peak distort; while2θ in50~60°range, diffraction peaks ofLnCC and LnSC have offset and fission; the synthetic products of Ln-Sr(or Ca)-Fe-O(referred to as LnS(C)F) are also the coexistence of CeO2cubic fluorite and perovskitephase. The bulk size of synthesis products is well-distributed with a spot of reunion. In theroom temperature to800℃, the change of conductivity of LnS(C)C and LnS(C)F cathodematerial is accordance with the p-type insulation pore small polaron theory. Arrhenius curvepresenting approximate linear in the low temperature period meets small polarons conductivemechanism; when the temperature is in charge of compensating conductive mechanism ofoxygen available, linear deflection, mainly by the semiconductor conductive type alsocorresponding to the transition metal type gradually, conductive metal typesemiconductor-change. In addition, the conductivity of LnS(C)C and LnS(C)F cathodematerials in the same conditions, the largest, LnSF595.15S/cm maximum conductivity, otherkinds of materials in the conductivity above500S/cm. Therefore, its performance meet the requirement of the cathode materials ITSOFC. And the LnS(C)F conductivity than LnS(C)C,because the conversion of Fe3+to Fe4+is much easier than Cu2+to Cu3+(because only inperovskite structure Cu3+is existing), the formation of Fe4+-O-Fe3+than the formation of poresmall polaron Cu3+-O-Cu2+pore small polaron easy to produce electronic compensation willbe relatively easily.Sol-gel method of CLO electrolyte materials synthesis temperature of900℃, the productof the system for the cubic fluorite crystal phase, cell parameters of the original0.54110nm toincrease0.54965nm(La3+into the cell), and the good dispersion, high-whiteness. In1400℃,CLO sintering samples of sintering3h relative density is more than95%. This material hashigh conductivity, is pure CeO2200times, when the ionic conductivity690℃can achieve0.066S/cm, meet temperature solid oxide fuel cell electrolyte material performancerequirements.