Sintering and grain growth of CoO-doped CeO2 ceramics

Co-doped CeO2 powders with atomic ratios equal to 0.25, 1 and 3% were synthesized by the conventional mixed-oxide method. No binary compounds were detected in the CeO2–CoO system, and the Co element exists as the state of Co2+ in the samples sintered above 1000°C. A small amount of Co doping reduces sintering temperatures and promotes grain boundary mobility dramatically. Over 99.0% of relative density (R.D.) can be obtained for 0.25% Co-doped sample sintered at 1300°C for 2 h, compared with ∼ 96% of relative density for pure CeO2 sintered at 1525°C for 2 h. The results from grain growth kinetics study indicate that grain growth exponent, n, and activation energy, Q, are 3 and 697 ± 37 kJ/mol for pure CeO2, 4 and 572 ± 57 kJ/mol for 0.25% Co-doped CeO2, respectively.