| Solid Oxide Fuel Cells(SOFC)was considered as a promising fuel cellbecause it is a kind of electricity generator with high efficiency and low pollution.As the key element of SOFC, in the performance of the whole cell, cathode plays avery important role. Its structure, character and mechanism of reaction will affectbehaviors of transmiting oxygen ions and electrical condu ctivity. For the furtherimprovement of cell performance, the developmenting high performance and novelcathode material is crucial.At present, SOFC operate commonly at about 1000℃.So it makes great sense to develop novel pattern of cathode materials with higherion and electrical conduetivity at intermediate temperature.The perovskite-like A2BO4 type oxide materials displayed mixed ionic andelectronic conducting properties, substantial oxygen permeability, highelectrochemical performance, and a relatively high oygen diffusion and surfaceexchange coefficients.In this thesis , the cathode material Sr2-xLnxMnO)4(Ln=Sm,Nd), x=(0, 0.1, 0.3, 0.5,0.7, 0.9) was synthesized by the sol-gel method. we studied the properties such asthe crystal structure, the chemistry compatibility of the electrode and electrolyte ,the match of TEC, intensity, TG, electrical conductivity and activation energy ofsample; investigated the microstructure, porterties sintered of sample, we determinethe optimum sintering temperature. appling ma terial to half cell, we studied theoutput characteristic. we come to the conclusion that both electrovalent balance andsolid solubility determine the cause shaping the struture of A2BO4 at x=0.3, 0.5.The sample has a good chemical compatibility with the GDC(Ce 0.9Gd0.1O1.9 ) within1100℃.In air, TEC of GDC was 17.7×10-6K-1 and sample was 17.7-19.3×10-6K-1 ,exhibiting the similar thermal expansion properties in the temperature range of 200-900℃.The loss of weight of sample result from overflowing H2O, interstitial O2-and lattice O. The electrical conductivity of sample that density was large increaseand activation energy decrease with x(x=0, 0.1, 0.3, 0.5, 0.7, 0.9) raising because ofconducting elelctric doublet increasing. The electrical conductivity of SSM1109 hasthe highest electrical conductivity reaching to 2.15 S·cm-1 and lowest activationenergy, 2.25 kJ·mol-1. Both the microstructure and sinter ing porterty of sampledetermine that the optimal sintering temperature was 1100℃. Electricalconductivity of sample synthesized at 1100℃increasing and interstitial O2-decreasing with x increasing determine overpotential of SSM1505 and SNM1505was lowest at 800℃when the current density of SSM1505 and SNM1505 that was 45mV and 38 mV respectively was equal. Appling material to half cell, it know fromproperties of sample that polariz ation resistance of cathode that decrease withtemperature increasing was proximiate to total polariz ation resistance which lead topower density increasing with temperature increasing. The highest output powerdensity was 333 mW/cm2 and 417mW/cm2 at 600℃and 650℃, respectively. |
