Phase Transformations in the Hafnia-Tantala-Titania System

非技术描述：该项目将通过在空气中进行高达2000摄氏度的高温X射线同步加速器衍射测量，研究氧化铪（HfO 2）-氧化钽（Ta 2 O 5）-氧化钛（TiO 2）基陶瓷的晶体结构变化机制。它还将研究如何通过化学添加剂稳定和控制结构变化。钽是一个有前途的候选人，以取代二氧化硅在微电子和集成微技术行业。其晶体结构之一有可能将其介电性能提高五个数量级。哈夫尼亚是一种超高温材料，在~2850摄氏度时熔化，可用作太空重返飞行器前缘的涂层。它具有更高的温度，晶体结构的变化类似于氧化锆（ZrO 2），这是能够增韧氧化锆基陶瓷，使它们不那么脆，但在更高的温度比氧化锆。少数民族（特别是女性）本科生将受到鼓励和指导，同时协助实验。技术专长：本项目将探索三元氧化物-氧化钽-氧化钛陶瓷系统，以阐明已知和新的相变机制。新开发的超高温、同步加速器和中子衍射技术，结合2800摄氏度的衍射仪，将用于在空气中原位获得定量晶体学信息。这将导致对化学掺杂剂的作用的理解，化学掺杂剂导致氧作为固溶体中的空位或间隙缺陷，从而导致相变的稳定或不稳定。下一代美国博士学生将在高能同步加速器（高级光子源）和中子衍射（Sputter-Neutron Source）国家设施中接受这种高度复杂的前沿研究技术的培训。

NON-TECHNICAL DESCRIPTION: This project will study the mechanism of crystal structure changes in hafnia (HfO2)-tantala (Ta2O5)-titania (TiO2) based ceramics by in situ high temperature X-ray synchrotron diffraction measurements up to 2000 degrees C in air. It will also investigate how to stabilize and control the structure changes through chemical additives. Tantala is a promising candidate to replace silica in the microelectronic and integrated microtechnology industries. One of its crystal structures has the potential to increase its dielectric properties by five orders of magnitude. Hafnia is an ultra high temperature material which melts at ~2850 degrees C and can be used as a coating on leading edges of re-entry vehicles from space. It has higher temperature, crystal structure changes analogous to zirconia (ZrO2), which are able to toughen zirconia-based ceramics and make them less brittle, but at higher temperatures than in zirconia. Minority (particularly women) undergraduate students will be encouraged and mentored while assisting with the experiments.TECHNICAL DETAILS:This project will explore the ternary hafnia-tantala-titania ceramic system to elucidate mechanisms of known and new phase transformations. Newly developed, ultra high temperature, synchrotron and neutron diffraction techniques, in conjunction with dilatometry to 2800 degrees C will be used to gain quantitative crystallographic information in situ, in air. This will lead to an understanding of the role of chemical dopants, which lead to oxygen as vacancy or interstitial defects in solid solution, resulting in stabilization or destabilization of phase transformations. The next generation of American Ph.D. students will be trained in such highly-sophisticated, forefront research techniques at high energy, synchrotron (Advanced Photon Source) and neutron diffraction (Spallation Neutron Source) national facilities.