The Study On The Electrolyte Materials Used For Solid Oxide Fuel Cell

Solid oxide fuel cell (SOFC) is a kind of green energy resource, and has many advantages of no corrosion, no leakage and fuel reforming in cell's interior. The electrolyte is the key component of SOFC. Therefore, the performance of SOFC system is determined by the properties of the electrolyte.YSZ (Y₂O₃ stabled ZrO₂) are usually used as the electrolyte material of SOFC because of high hot stability, chemistry stability, excellent mechanics function and pure oxygen ionic conduction in very wide oxygen partials. In this thesis, the YSZ nano-powder was synthesized by hydrothermal method. The influence of predecessor, precipitator, precipitator concentration, and mineralizer on properties of powder and sintered body are studied in details. The results show that the predecessor has a great influence on the crystal structure of YSZ powder, and the conductivity of YSZ is 0.034 S/cm at 800℃.SSZ (Sc2O3 stabled ZrO₂) has a high conductivity at low temperature, and shows a vast range of prospects for development in intermediate temperature SOFC. The process parameters and sintering temperature were use to study the effect of microstructure, crystal structure and properties of SSZ. The results indicate that monodisperse spherical SSZ powder of diameter 6⁹nm were prepared using NaOH precipitator, and the relative density of sintered body at 1500℃is 97.3%. The conductivity of 8SSZ is 0.23S/cm at 900℃and 0.13S/cm at 800℃, and is superior to 10SSZ and 12SSZ withβphase.In addition, Y₂O₃-Al2O3, Sc2O3-Al2O3, Y₂O₃-Sc2O3 doped ZrO₂ were investigated by contrastive study. For Al2O3 doped YSZ and SSZ, the grain size of powder was refined, the apparent density was increased, and has a gently aggregation. The mechanical properties were improved, but the electrical property was decreased. The fracture strength of SSZA is 265.5MPa, but the conductivity of 0.185S/cm at 900℃is lower than that of SSZ. The electrical and mechanical properties were between YSZ and SSZ.Moreover, the deposition technique, sinterability and electrical property of SSZ thin film were discussed. The results show that the modified dry pressing process is simple and efficient. But the electrolyte films are easily stripped from anode substrate, and the conductivity is 0.0981S/cm at 800℃. The thickness of films grown by hydrothermal is at a range of about 10⁵0μm, and the adhesion of coating is very good. The conductivity is 0.071S/cm at 800℃, and the activation energy for conduction is lower than that of sintered body and films grown by dry pressing process.