The microstructure, thermal expansion, mechanical property, and ionic conductivity of samaria-doped ceria (SDC) prepared by coprecipitation were investigated in this paper. The results revealed that the average particle size ranged from 10.9±0.4 to 13.5±0.5 nm, crystallite dimension varied from 8.6±0.3 to 10.7±0.4 nm, and the specific surface area distribution ranged from 62.6±1.8 to 76.7±2.2 m2/g for SDC powders prepared by coprecipitation. The dependence of lattice parameter, a, versus dopant concentration, x, of Sm3+ ion shows that these solid solutions obey Vegard's rule as a (x)=5.4089+0.10743x for Ce1−xSmxO2−1/2x. For SDC ceramics sintered at 1500°C for 5 h, the bulk density was over 95% of the theoretical density; the maximum ionic conductivity, 800°C=(22.3±1.14) × 10−3 S/cm with minimum activation energy, Ea=0.89±0.02 eV, was found in the Ce0.80Sm0.20O1.90 ceramic. A dense Ce0.8Sm0.2O1.9 ceramic with a grain size distribution of 0.5–4 m can be obtained by controlling the soaking time at 1500°C. When the soaking time was increased, the microhardness of Ce0.8Sm0.2O1.9 ceramic increased, the toughness slightly decreased, which was related to grain growth with the soaking time.
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Document Type: Research Article
Department of Materials Science and Engineering, National Dong-Hwa University, Hualien, 974 Taiwan
Department of Resources Engineering, National Cheng Kung University, Tainan 701, Taiwan
Publication date: January 1, 2008