|About this Abstract
||Materials Science & Technology 2019
||Phase Transformations in Ceramics: Science and Applications
||Topotactic Motif and Orientation Relation Extraction for Phase Transformations from In-Situ X-ray Powder Diffraction
||Scott J. Mc Cormack, Waltraud M. Kriven
|On-Site Speaker (Planned)
||Waltraud M. Kriven
In-situ high temperature synchrotron, X-ray powder diffraction was used to extract the topotactic motif and orientation relationship between the orthorhombic Hf6Ta2O17 (Ima2, S.G. 46) and tetragonal HfO2 (P42/nmc, S.G. 137) peritectic reaction at ~2250 ˚C:
Hf6Ta2O17 (Orthorhombic, Ima2) forms HfO2 (Tetragonal,P42/nmc) + L (Hf,Ta,O).
The topotactic relationship for the peritectic reaction was obtained from continuous Bragg peaks through the peritectic transformation. These Bragg peaks arose from a face-centered, Z=4, pseudo-cell, cation Motif that was present in both the parent (tetragonal HfO2) and the product (orthorhombic Hf6Ta2O17) phases. The continuous Bragg peaks defined by using reciprocal vectors in terms of the parent (HfO2) structure were minimized in strain when compared with the product (Hf6Ta2O17) structure. These constituted the reciprocal basis vectors from which the orientation relationship could be extracted so as to align the Hf6Ta2O17 crystal with the HfO2 crystal.
||Definite: At-meeting proceedings