b'Phase stability of yttriumYttrium titanium oxides show newly discovered stable cubic and titanium oxides hexagonal phases up to 1200C, which has implications on their material behavior and performance in nuclear environments.T his project had two main goals: 1) understand the phase stability and high temperature phase transition of yttrium titanium oxides and 2) use state-of-the-art high temperature in situ x-ray diffraction and transmission electron microscopy techniques to create a new workflow for correlative characterization to PROJECT NUMBER:understand material behaviors under extreme environment in the context of nuclear 22P1065-024FP technology development. The results were not what we expected. We observed hexagonal crystal structure for two of the yttrium titanium oxide compositions that are TOTAL APPROVED AMOUNT:not widely documented in the literature. Although the cubic and hexagonal phases are $135,000 over 1 year high temperature phases according to published phase diagrams, they did not convert PRINCIPAL INVESTIGATOR:into the orthorhombic phase that was supposed to be the stable phase at ambient Kaustubh Bawane temperature. This exciting new discovery created challenges for x-ray diffraction and transmission electron microscopy quantification due to the lack of high-quality CO-INVESTIGATORS: references in the literature. It is possible the hexagonal and cubic phases are more Xiaofei Pu, INL stable at lower temperature conditions (1200C) than previously documented, which Honggyu Kim, University of Florida would have implications to material behaviors and performance at high temperature Lingfeng He, North Carolina State University conditions in the context of nuclear structural materials and nuclear waste forms. Despite the unexpected observations, correlative characterization between x-ray diffraction, transmission electron microscopy, and scanning electron microscopy electron backscatter diffraction were conducted in this study and set up the stage for future investigation on different materials.136'