DESIGN OF CERAMICS BY COTROLLING GRAIN BOUNDARY CHARACTER AND QUANTUM STRUCTURES

用双晶和三晶研究氧化物陶瓷中晶界特征对性能的影响。系统地制备了Al_2O_3，ZrO_2，ZnO和SrTiO_3四种双晶材料，并用高分辨电子显微镜（HREM）、电子能量损失谱（EELS）和能谱仪（EDS）对材料的晶界原子结构、化学键状态和成分进行了表征。此外，还测量了双晶的晶界能、蠕变行为和电子性质，从晶界特征的角度阐明了晶界结构、化学和性质之间的关系。结合高分辨电子显微术和静态晶格计算，分析了各双晶体中的晶界结构。高分辨透射电镜观察表明，晶界具有沿晶界面沿着平移的非对称结构。静态点阵计算得到的最稳定晶界模型与高分辨电镜图像吻合较好。结果发现， ...更多信息 晶界面是决定晶界原子结构重要因素。通过高温压缩蠕变试验研究了合金的晶界滑移行为。晶界滑移的蠕变行为取决于晶界结构和原子密度。纯氧化铝中的[0001]倾斜晶界沿着界面含有大的开放空间。在氧化铝中的Y掺杂的边界也表现出类似的核心结构，表明Y离子偏析没有改变晶界结构，即使在原子水平。此外，静态晶格计算表明，Y离子往往位于周围的开放空间在晶界核心。因此，它被认为是Y离子发挥作用，降低原子扩散率在开放的晶界核心，即使当它们的浓度是相当小的。在此基础上，定量地认识了晶界原子结构和特征的重要性，并提出了陶瓷晶界设计的指导原则。少

The effect of grain boundary character on the properties in oxide ceramics by using bicrystals and tricrystals. The bicrystals of Al_2O_3,ZrO_2,ZnO and SrTiO_3 have systematically fabricated, and the grain boundary atomic structures, chemical bonding state and composition were characterized by HREM, EELS and EDS. In addition, the grain boundary energy, creep behavior and electronic properties in the respective bicrystals were measured, and the relationships of grain boundary structures, chemistry and properties were clarified from the view point of grain boundary character. The grain boundary structures in the respective bicrystals were thus analyzed by combination of HREM and static lattice calculation. HRTEM observation revealed that the present grain boundaries have asymmetrical structures with translation along the grain boundary plane. The most stable grain boundary models calculated by static lattice calculation well correspond with the HREM image. It was found that characters of … More grain boundary plane are an important factor to determine grain boundary atomic structures. The behavior of grain boundary sliding was also investigated by high temperature compressive creep test. The creep behavior due to grain boundary sliding was found to depend on the grain boundary structures and atomic density The [0001] tilt grain boundaries in pure alumina contained large open spaces along the boundary plane. The Y-doped boundary in alumina also exhibited a similar core structure, indicating that Y ions segregation did not change the grain boundary structure even at the atomic level. In addition, static lattice calculations showed that Y ions tended to be located around the open spaces at the grain boundary core. Therefore, it is thought that Y ions play a role for decreasing atomic diffusivity at the open grain boundary core even when their concentration is quite small. Based on the results mentioned above, importance of grain boundary atomic structures and characters were quantitatively understood, and an guideline to design ceramic grain boundary were proposed in this study. Less