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Preparation and Characterization of La0.8Sr0.2Co1-yFeyO3 for Cathode by PVA Method

Author: XingChangSheng
Tutor: QianXiaoLiang
School: Huazhong University of Science and Technology
Course: Environmental Science
Keywords: The solid oxide fuel cell Perovskite Cathode Conductivity Nano AC impedance
CLC: O611.3
Type: Master's thesis
Year: 2004
Downloads: 173
Quote: 1
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Abstract


Perovskite structure La 1-x the Sr x the Co. 1-y FeyO 3 (LSCF) has excellent electron - ion mixed conductivity properties, widely used in fuel cells, gas sensors, membrane catalysis, oxygen separation. Of LSCF preparation cost is expensive, the process is complicated, it is difficult to meet the requirements of large-scale commercial applications. Discuss the preparation of perovskite materials in the system based on the study of the citric acid method as the basis for proposed new liquid phase method with prospects for industrial applications - PVA method is not only easy to process, but also greatly reduces the the milling costs; research laboratory milling process of the law, and provides important parameters for their industrial applications. The citric acid method and PVA prepared La 0.8 Sr 0.2 Co 1-y FeyO 3 powder. Research results show that during the synthesis of the citric acid, the molar ratio of citric acid with a metal ion, the pH of the precursor body fluids value, into the composition of the glue temperature on the formation of gels and powders, the crystal structure has a significant impact; PVA Synthesis process, the degree of polymerization (DP value), the number of the metal ion charge adjuvants Ax-molar ratio, the gelation temperature of the formation of the dry gel, the powder materials have a significant impact on performance. PVA synthesis process conditions determined by experiment, comparison, PVA than citrate method has the advantages of low-cost, short production cycle, operability. Using TG-DTA, IR, XRD study powder synthesis process found that citric acid method and PVA method similar to the preparation of the LSCF the mechanism: With the evaporation of water, the carbon skeleton and nitrate occurred partially decompose and emit a lot of CO2 gas, it combined with SrO generate intermediate phase SrCO 3 ; organics and nitrate decomposition when the temperature reaches 600 ° C, 800 ℃ for 2h to obtain a single perovskite phase. SEM, TEM photographs show that citrate powder prepared a wide particle size range, the PVA prepared by the powder particle size uniformity; citric large specific surface area than the PVA SYSTEM prepared powders prepared powder, by the two methods The powder prepared are nanoscale. DC voltammetry and AC impedance studies PVA prepared La 0.8 Sr 0.2 the Co. 1-of y FeyO, 3 < / sub> ceramic electronic conductivity and ionic conductivity. The results show that: under the same conditions, La 0.8 Sr 0.2 the Co. 1-Y FeyO 3 of the electronic conductivity. With the sintered material to elevated molding temperature is increased, with the increase of the Co content increases; as the temperature rises, the La 0.8 Sr 0.2 Co < sub> 1-y FeyO 3 electronic conductivity peaks, a slow increase in the low-temperature phase, in line with the small polaron conduction mechanisms. The ionic conductivity is increased as the temperature increases, with the increase of the Co content increases. In the low-temperature phase of the charge displacement is the rate-limiting step of the electrode process; charge transfer and gas diffusion electrode process rate-controlling step in the high-temperature phase. 700 ℃, La 0.8 Sr , Co. , 0.2 0.9 Fe 0.1 O 3 of The ionic conductivity of 0.043 S · cm-1, at 800 ° C, La 0.8 Sr , Co. , 0.2 0.5 Fe 0.5 O 3 , the electronic conductivity of 386 S? cm-1, able to meet the requirements of the medium-temperature fuel cell. Other properties of materials: La 0.8 Sr 0.2 Co 1-y FeyO 3 Materials and GDC materials has a good high

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CLC: > Mathematical sciences and chemical > Chemistry > Inorganic Chemistry > Chemical elements and inorganic compounds > Nature
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