Oxide Doped Of Ce <sub> 0.9 </ Sub> Re <sub> 0.1 </ Sub> O <sub> 2-¦Ä </ Sub> (re = Sm, Gd) Ceramic Material Structure And Electrical Properties,

Solid oxide fuel cells (SOFCs) have been considered as power generation devices in the future as they have demonstrated high energy-conversion efficiency, high power density and extremely low pollution, in addition to flexibility in using hydrocarbon fuels. This application typically requires conduction of oxygen ions which narrows the candidate materials to solid oxide electrolytes. To date,yttria-stabilised zirconia (YSZ) has been mainly used as the solid oxide electrolyte for such fuel cells because of its nearly pure oxygen ionic conductivity in an oxidizing or a reducing atmosphere and its good mechanical properties. However, high operating temperatures of over 900℃are required for this electrolyte because of its relatively limited oxide ion conductivity. This condition increases the fabrication cost and accelerates degradation of the fuel-cell system. Ceria-based solid solutions have higher oxygen-ion conductivity than that of YSZ at intermediate (500-700℃) temperatures and they have been regarded as the most promising electrolytes for intermediate temperature SOFC (IT-SOFC). Doped-CeO2 based electrolyte was considered as the most potential applications in solid oxide fuel cells for its high ionic conductivity and low active energy. The ionic conductivities of ceria-based electrolytes, doped with various cations (e.g., Ca2+, Sr2+, Y3+, La3+, Nd3+, Gd3+ and Sm3+) at different dopant concentrations, have been extensively studied. And recently, the grain boundary performance of the transition oxide doped Sm2O3 or Gd2O3 doped CeO2 content 500ppm impure systems has been systematically investigated, while added different content scavenger (MgO, ZnO), although some literature data are available regarding the ionic conductivities as a function of dopant contents.(1) The precursor powder of Ce0.9Sm0.102-δwhich contents500×10-6SiO2 impurity(SDCSi), was prepared by sol-gel, and 0-3.0 mol% MgO have been loaded into the SDCSi powders, respectively. The effects of doping level, and sintering temperature on the sintering property, microstructure and electrical properties of SDCSi ceramics were investigated by X-ray Diffraction(X-RD), Field Emission Scanning Electronic Microscopy (FE-SEM) and AC impedance spectroscopy observation. It has been found that MgO is not only can reduced the sintering temperature about 100-200℃of SDCSi, but also can increase the relative density of the ceramics. It was also found that MgO can mitigate the harmful effects of SiO2 impurity to have a positive effect on grain boundary (GB) conductivity of SDCSi ceramics. The grain boundary conduction increase markedly in the present work for the 1.0 mol% MgO-loaded SDCSi ceramics. In this paper we found that MgO is a effective sintering aid, and can use as a new scavenger of grain boundary.(2) the precursor powder of Ce0.9Gd0.1O2-δceramics with 500 X 10-6 SiO2 (GDCSi) was prepared by sol-gel method.0.1-3 at.% ZnO was added into the precursors by the form of Zn(NO3)2·6H2O. The effects of doping level on the sintering property and microstructure of GDCSi ceramics were investigated by means of X-ray diffraction (X-RD) and field-emission scanning electron microscopy(FE-SEM) observation. In the ZnO content range used, the sintering temperature decreased consistently with increasing ZnO level. Small additions of ZnO promoted the relative densification significantly. The relative densification reached a maximum at 1.0 at.% ZnO, then unchangeable with further increase in ZnO content. The ZnO doping level was also found to have a remarkable influence on the grain growth behavior, which depended on sintering temperature. ZnO loading was also found to have a positive effect on grain boundary(GB) conductivity of GDCSi ceramics. the combination of silica with ZnO led to a significant deterioration to the GB effect compared with silica alone. The ZnO dopant exhibited the optimal scavenging effect in the temperature range of 1400-1500℃, in which a higher GB conductivity was achieved for GDCSi ceramics.