Phase Transformations in the Hafnia-Tantala-Titania System

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

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.