Phase Transformations in the Hafnia-Tantala-Titania System

非技术描述：本项目将通过在空气中高达2000℃的高温X射线同步衍射测量来研究Hafnia(HfO2)-Tantala(Ta2O5)-TiO2(二氧化钛)基陶瓷的晶体结构变化机理。它还将研究如何通过化学添加剂稳定和控制结构变化。在微电子和集成微技术行业中，坦塔拉是很有希望取代二氧化硅的候选材料。它的一种晶体结构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摄氏度熔化，可用作太空再入飞行器前缘的涂层。它具有更高的温度，晶体结构变化类似于氧化锆(ZrO2)，能够增韧氧化锆基陶瓷，使其不那么脆化，但温度比氧化锆高。少数族裔(尤其是女性)本科生将在协助实验的同时受到鼓励和指导。技术细节：本项目将探索Hafnia-Tantala-TiO2三元陶瓷系统，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，与2800摄氏度的膨胀法相结合，将在空气中原位获得定量的结晶学信息。这将有助于理解化学掺杂剂的作用，它会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失稳。下一代美国博士生将在高能、同步加速器(高级光子源)和中子衍射(散裂中子源)国家设施中接受这种高度尖端的研究技术培训。

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.