| Solid oxide fuel cell (SOFC), which is an all solid device to convert the chemical energy of the fuel into electrical energy directly, has been played great attention duo to high efficiency and environmental protection. Currently, the development tendency for SOFC is lower the operating temperature (the operating temperature below800℃). In order to obtain the excellent output performance, employing an electrolyte material with high conductivity (La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM)) and the technologies for electrolyte layer to be film is a very promising technology route.In this paper, the single cells were supported by porous anode substrates, and the electrolyte layers were prepared to be film by the film-technologies. Firstly. La0.7Sr0.3Cr0.5Mn0.5O3-δ (LSCM) anode powder and La0.4Ce0.6O2-δ(LDC) powder were synthesized by glycine nitrate process (GNP). And the LSCM crystal structure, bond length and density of states (DOS) were simulated by Materials Studio software. And the LSCM anode powder mixed with three types of pore-formers with different amounts, the mixtures were pressed into pellets by five pressures.8wt.%starch as the pore-former has the best the capability for porosity, when the pressure at10MPa, the maximum porosity of the anode was45%. LDC powders and NiO powders was mixed to be composite anode materials with different ratios, after mixing with pore formers, the mixtures were sintered to form pore anode pellets, and the particles of the anode materials were very well. When the ratio of LDC and NiO was5:5, the porosity was about30%, and the conductivity of the anode pellet was the highest at800℃Next, the LSGM electrolyte films were prepared by radio frequency magnetron sputtering and slurry spin coating on LSCM and NiO-LDC porous anode substrate, respectively, and the parameters of the preparing films were explored. In the sputtering process for LSGM film, the substrate temperature. Ar pressure and depositing power for the film were explored, and the optimum process parameters for the film deposited by magnetron sputtering:sputtering pressure is5Pa, depositing power is210W, substrate temperature is300℃, annealing temperature is1000℃, annealing time is2h. Depositing with the optimized process parameters. LSGM film was very dense, the crystallinity of the film was very good, and the film adhered to the substrate closely. The study illustrated that the deposited rate becomes less and the particle size of the film become greater when the substrate temperature was higher.The deposited mechanism was also discussed. The film was deposited on Si pellets in1,3and5min, respectively. The research showed that LSGM electrolyte film was deposited with island growth mode, and the film appeared phenomenon of preferential growth. After annealing, the phenomenon of preferential growth and the uneven film were disappeared. The results of slurry spin coating showed that a dense film can be obtained by employing the process parameters:5wt.%Ethyl cellulose as a binder.5wt.%Terpineol as moderator agent repeating spin9times and sintering at1400℃for4h.In order to research the process of O2-conduction in LSGM crystal, the LSGM crystal structure, bond length and density of state were calculated and simulated by the Materials Studio software, and the transfer process dynamics of O2-in LSGM crystal was also simulated. The research found that the O2-which formed bond with Ga/Mg in La90Sr10Ga80Mg20O287crystal was very easy to transfer. The transfer energy of the O2-was also calculated though analysis of the transition process. The transfer energies of the O2" which formed bond with Ga and Mg were-0.152eV and-0.232eV, respectively, which was benefit to the transfer of O2-Finally, the LSGM electrolyte layer were fabricated by magnetron sputtering and slurry spin coating on LSCM or NiO-LDC anode substrate, and four kinds of single cells were prepared, and the cross-sectional morphologies, AC impedance, open circuit voltage (OCV) and power density of the cells were explored. The studies illustrated that the film prepared by magnetron sputtering was dense and uniform, adhered to anode substrates closely, and the AC impedance of the single cell was small, especially for the single cell of NiO-LDC/LSGM/LSCF. If the cell prepared by sputtering, the polarization resistivty and ohmic resistivity of the single cell prepared by magnetron sputtering were0.14Ω·cm2and0.74Ω·cm2respectively. And the polarization resistivty and ohmic resistivity of the single cell prepared by spin coating were3.23Ω·cm2and1.8Ω·cm2respectively. Regardless of the LSCM or NiO-LDC porous anode substate. the polarization resistivity of the cell prepared by magnetron sputtering was less than the ohmic resistivity of it, however the polarization resistivity of the cell prepared by spin coating was larger than the ohmic resistivity of it.The open circuit voltage of the LSCM (supported)/LSGM/LSCF single cell was great, and the maximum was1.09V, which was very close to the theoretical value. The open circuit voltage of NiO-LDC (supported)/LSGM/LSCF single cell was small, the OCV at high temperature was about0.7V, however, the largest current and largest power of the NiO-LDC (supported)/LSGM/LSCF single cell were very well. The largest current density and power density of the single cells prepared by magnetron sputtering and slurry spin coating were370.71mA/cm2,71.23mW/cm2and290.72mA/cm2,44.12mW/cm2, respectively. In a word, the structure and performance of the single cell prepared by magnetron sputtering are better than those prepared by slurry spin coating. |
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