Characteristics of Ceris-Doped Tetragonal Zirconia Powders Prepared Using Alcohol as a Crystallization Solvent

为了提高掺铈四方氧化锆的烧结性能和力学性能，采用氨共沉淀法制备了非晶CeO_2-ZrO_2凝胶，并用超临界甲醇对其进行了结晶和干燥。凝胶在空气中煅烧结晶的温度为420^oC，而在水和有机溶剂（如甲醇）存在下结晶的温度为200^oC至250^oC。CeO_2-ZrO_2粉末的烧结性能对结晶条件较为敏感，沉淀凝胶在空气中正常焙烧结晶时形成硬团块，而在水和有机溶剂中结晶时形成软团块。在250^oC的甲醇和水中结晶的CeO_2-ZrO_2粉末分别在1150^oC和1400^oC时烧结到完全理论密度，而在450^oC的空气中煅烧结晶的CeO_2-ZrO_2粉末即使在1500^oC时也只能烧结到理论密度的95.2%。在甲醇中结晶的CeO_2-ZrO_2的断裂强度远高于在水和空气中结晶的CeO_2-ZrO_2，并且随着超临界干燥和/或在ZrO_2晶界处分散MnO、Al_2O_3和CeMnAl_<11>O_<19>等氧化物颗粒而增加。

In oder to improve the sinterbility and mechanical properties of ceria-doped tetragonal zirconia, amorphus CeO_2-ZrO_2 gels prepared by coprecipitation in ammonia solutions were crystallized and dried using supercritical methanol. The onset of crystallization of the gels, from calcining in air was 420^oC, while 200^oC to 250^oC in the presence of water and organic solvents such as methanol. The sintering behavious of CeO_2-ZrO_2 powders were sensitive to the crystallizing conditions, since hard agglomerates formed when the precipitated gels were crystallized by normal calcination in air, wheras soft agglomerates formed when they were crystallized in water and organic solvent. CeO_2-ZrO_2 powders crystallized in methanol and water at 250^oC were sintered to full theoretical density at 1150^oC and 1400^oC, respectively, whereas that crystallized by calcination in air at 450^oC was sintered to only 95.2% of theoretical density, even at 1500^oC.Fracture strengths of CeO_2-ZrO_2 fabricated using the powders crystallized in methanol were much higher than those crystallized in water and air and increased with supercritical drying and/or dispersing oxide particles such as MnO, Al_2O_3 and CeMnAl_<11>O_<19> at the grain boundary of ZrO_2.