Low-temperature fabrication and electrical property of 10 mol% Sm2O3-doped CeO2 ceramics

Ten mol% Sm2O3-doped CeO2 solid-solution (20SDC) powders have been synthesized via carbonate coprecipitation using ammonium hydrogen carbonate (AHC) and urea as the precipitants, respectively. Characterizations were achieved by elemental analysis, X-ray diffractometry, differential thermal analysis/thermogravimetry, and FESEM. An amorphous hydroxyl carbonate precursor (Ce, Sm)(OH)CO3 center dot 2H(2)O having nanosized (similar to 10 nm) spherical particles was formed with AHC, while a mixture of crystalline (Ce, Sm)(2)(CO3)(2)(OH)(2)center dot H2O and (Ce, Sm)(2)O(CO3)(2)center dot H2O phases exhibiting irregular particle morphologies was obtained with urea. Both the precursors convert to oxide solid solutions without any phase detected corresponding to Sm2O3 during calcination. The oxide powder processed via the AHC method can be sintered to >99% of the theoretical at a low temperature of 1200 degrees C, due to the good dispersion and ultrafine size (similar to 15 nm) of the particles, while that from the urea method can only reach similar to 67.2% dense at the same temperature. Electrical conductivity of the densified ceramic was measured in air in the range 400-700 degrees C by the DC three-point method, and an activation energy of similar to 60.5 kJ/mol was derived from the experimental data. (C) 2003 Elsevier Ltd. All rights reserved.