Structure Control and Thermal Stability of Tetragonal Zirconia by Post-HIPing Method

采用后烧成热等静压的方法，研究了提高四方氧化锆多晶的热稳定性和控制其微观结构。本研究的目的是通过对陶瓷的微观结构进行控制，获得具有高断裂强度、高断裂韧性、高热稳定性和高抗热震性能的(Y，Ce)-TZP/Al_2O_3复相陶瓷、(Y，Ce)-TZP/Al_2O_3复相陶瓷、Ce-TZP复相陶瓷和Ce-TZP/Al_2O_3复相陶瓷。然后在100~150ﾟ和1300~1600 Mpa的压力下采用热等静压的方法来减小流动尺寸，控制烧结体的显微组织。从TZP陶瓷的晶相和显微结构的变化以及断裂强度的退化情况来看，细化氧化锆晶粒度、弥散Al_2O_3和CeO_2合金化可以提高氧化锆陶瓷的热稳定性。当CeO_2的合金化含量超过12%时，Y-TZP陶瓷的热稳定性可以得到很好的控制，但显著降低了陶瓷的烧结性和断裂强度。Al_2O_3颗粒的分散可以改善(Y，Ce)-TZP的力学性能。热等静压后处理有利于(Y，Ce)-TZP/Al_2O_3复合材料的致密化和力学性能的提高。烧结后热等静压有利于Ce-TZP/Al_2O_3复合材料的致密化而不长大，提高断裂强度和抗热震性能。结果表明，采用后热等静压法制备的四方氧化锆基陶瓷具有热稳定性好、断裂强度高、抗热震性好等特点。

Improvement of thermal stability and control in the microstructure of tetragonal zirconia polycrystals were studied by the application of the postsintering hot isostatic pressing method. The goal of the present study is to obtain the fundamental results on fabrication of the yttria and ceria doped tetragonal zirconia polycrystals ((Y,Ce)-TZP), (Y,Ce)-TZP/Al_2O_3 composites, ceria doped tetragonal zirconia polycrystals (Ce-TZP) and Ce-TZP/Al_2O_3 composites with high fracture strength, high fracture toughness, high thermal stability and high thermal shock resistance by controlling the microstructure of these ceramics.The present tetragonal zirconia based ceramics were fabricated at 1400-1500ﾟC for 10hr in air,,and then postsintering hot isostatic pressing method was applied at 100-15OMPa and 1300-1600ﾟC for lhr in order to decrease the flow size and to control the microstructure of these sintered bodies. From the results on changes in the crystalline phase and microstructure and degradation of fracture strength of TZP ceramics, the thermal stability of zirconia could be improved by decreasing the grain size of zirconia, dispersing Al_2O_3 and alloying with CeO_2. Thermal stability of Y-TZP ceramics could be perfectly controlled by alloying with more than 12 mol% CeO_2, but it significantly degradated the sinterability, and fracture strength . The mechanical properties of (Y,Ce)-TZP could be improved by dispersing Al_2O_3 particles. Post-HIP method was useful to densify the (Y,Ce)-TZP/Al_2O_3 composites and to improve their mechanical properties. Postsintering hot isostatic pressing was very useful to densify Ce-TZP/Al_2O_3 composites without grain growth and to improve the fracture-strength and thermal shock resistance. It is found that the tetragonal ZrO_2 based ceramics with thermal stability, high fracture strength and good thermal shock resistance are easily fabricated by post-HIPing method.