Design of the high-temperature ceramic materials by small amount of dopant addition

少量掺杂剂高温陶瓷材料的设计

基本信息

批准号：
10450254
负责人：
SAKUMA Taketo
金额：
$ 9.02万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

In this research the high-temperature mechanical properties in engineering ceramic materials such as polycrystalline Al_2O_3 was examined. It was found that the doping of trivalent ions such as Y or Lu is very effective to improve the high-temperature creep resistance in Al_2O_3 ceramics. On the other hand, some of divalent or tetravalent ions reduce the creep resistance in Al_2O_3. The origin of the dopant effect was revealed by using transmission electron microscopy, especially high-resolution transmission electron microscopy. By using high-resolution transmission electron microscccpy and attached EELS (electron energy loss spectroscopy) or EDS (energy dispersive X-ray spectroscopy) analysis, it has been found in the present work that the doped cations tend to segregate at the grain boundary, and change chemical bonding state at the grain boundaries. The segregation was detected in uniformly in the oxide ceramics by STEM (Scanning TEM)-EDS method. The change in the chemical bonding state was able to be quantitatively estimated by the first-principle molecular orbital calculations. For example, from the calculation of DOS (density of states in unoccupied molecular orbital) the experimental EELS spectra can be explained, and it was found that the change in the EELS means that the ionicity at the grain boundary is increased due to the dopant cation segregation. Moreover, it is revealed that the improved creep resistance in cation-doped oxide ceramics results from the increment in the atomic bonding strength. The present results would bring an important and ultimately new method to develop high-temperature ceramic materials.

在这项研究中，检查了工程陶瓷材料（例如多晶AL_2O_3）中的高温机械性能。已经发现，诸如y或lu之类的三价离子的掺杂对于改善Al_2O_3陶瓷中的高温蠕变耐药性非常有效。另一方面，某些二价或四位数离子降低了al_2o_3中的蠕变抗性。通过使用透射电子显微镜，尤其是高分辨率透射电子显微镜，可以揭示掺杂剂效应的起源。通过使用高分辨率透射电子微循环和附着的鳗鱼（电子能量损失光谱）或EDS（能量分散X射线光谱分析），在本工作中已经发现，掺杂的阳离子倾向于在晶界处隔离，并在晶界改变化学键合状态。通过茎（扫描TEM）-EDS方法在氧化陶瓷中均匀地检测到隔离。化学键合状态的变化能够通过第一本分子轨道计算来定量估计。例如，从DOS的计算（未占用分子轨道的状态的密度）可以解释实验鳗鱼光谱，并且发现鳗鱼的变化意味着晶界的离子性因掺杂剂阳离子的隔离而增加。此外，据表明，阳离子掺杂氧化物陶瓷的蠕变耐药性改善是由于原子键合强度的增长而导致的。目前的结果将带来一种重要的新方法来开发高温陶瓷材料。