Editorial: Ordered and disordered cubic systems: pyrochlore to fluorite, now and the horizon
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Date
2022-01-12
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Frontiers Media S.A.
Abstract
Any internet search for the term pyrochlore, fluorite or the derivation of the two will yield tens of thousands of results. This is clear evidence that the study of these systems, especially since the publication of the landmark review by Subramanian et al. (1983) in 1983 increases with every passing year.
The minerals fluorite and pyrochlore can be thought of as two ends of a continuum that encompass other variations such as defect fluorite. Materials with a fluorite structure are used in a wide range of applications, one reason being its ability to incorporate structural disorder. A cubic structure is the simplest in terms of symmetry and thus can accommodate certain amounts of variation in occupancy of atomic positions over a range of different crystallographic sites. It is this versatility that has seen these humble structures applied to all manner of uses ranging from fuel in a nuclear reactor (Simeone et al., 2017), fuel cell anodes (Lang et al., 2009), ion conductors (Wilde and Catlow, 1998), nuclear waste immobilization (Ewing et al., 2004), thermal barrier coatings (Wilde and Catlow, 1998), catalysts (Kim et al., 2020), and superconductors (Yonezawa et al., 2004) to name only a few. Often there is a common thread in these publications which is investigating in one form or another the order or disorder in those systems with one extreme example being high entropy pyrochlores (Oses et al., 2020).
It was our goal with this special edition to give an overview of what has traditionally been thought to be disorder in pyrochlore, how it relates to defect fluorite, to highlight the newest discoveries as well as the path forward in this research area. We included the effect of order or disorder induced by external means (irradiation, ball milling, pressure, and temperature), induced internally (changes in chemical composition and stoichiometry) and studies that advance the understanding of disorder occurring in those systems and the effect it has on the structure and properties. These studies were planned to encompass experimental, theoretical (such a density functional theory modelling) or a combination of both studies as is common in the current literature. Copyright © 2022 Thorogood, Finkeldei, Lang and Simeone. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY).
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Keywords
Pyrochlore, Fluorite, Materials, Cubic lattices, Crystals, Order-disorder transformations
Citation
Thorogood, G. J., Finkeldei, S. C., Lang, M. K., & Simeone, D. (2021). Editorial: Ordered and disordered cubic systems: pyrochlore to fluorite, now and the horizon. Frontiers in Chemistry, 9, 830330. doi:10.3389/fchem.2021.830330