Long- and short-range orders in 10-component compositionally complex ceramics

Dawei Zhang; Yan Chen; Heidy Vega; Tianshi Feng; Dunji Yu; Michelle Everett; Joerg Neuefeind; Ke An; Renkun Chen; Jian Luo

doi:10.1016/j.apmate.2022.100098

Long- and short-range orders in 10-component compositionally complex ceramics

Dawei Zhang, Yan Chen, Heidy Vega, Tianshi Feng, Dunji Yu, Michelle Everett, Joerg Neuefeind, Ke An, Renkun Chen, Jian Luo

Research output: Contribution to journal › Article › peer-review

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Abstract

Neutron diffraction and total scattering are combined to investigate a series of single-phase 10-component compositionally complex fluorite-based oxides, [(Pr_0.375Nd_0.375Yb_0.25)₂(Ti_0.5Hf_0.25Zr_0.25)₂O₇]_1-x[(DyHoErNb)O₇]_x, denoted as 10CCFBO_xNb. A long-range order-disorder transition (ODT) occurs at x = 0.81 ± 0.01 from the ordered pyrochlore to disordered defect fluorite. In contrast to ternary oxides, this ODT occurs abruptly without an observable two-phase region; moreover, the phase stability in 10CCFBOs deviates from the well-established criteria for simpler oxides. Rietveld refinements of neutron diffraction patterns suggest that this ODT occurs via the migration of oxygen anions from the position 48f to 8a, with a small final jump at the ODT; however, the 8a oxygen occupancy changes gradually (without an observable discontinuous jump). We further discover diffuse scattering in Nb-rich compositions, which suggests the presence of short-range order. Using small-box modelling, four compositions near ODT (x = 0.75, 0.8, 0.85, and 1) can be better fitted by C222₁ weberite ordering for the local polyhedral structure at nanoscale. Interestingly, 10CCFBO_0.75Nb and 10CCFBO_0.8Nb possess both long-range pyrochlore order and short-range weberite-type order, which can be understood from severe local distortion of the pyrochlore polyhedral structure. Thus, weberite-type short-range order emerges before the ODT, coexisting and interacting with long-range pyrochlore order. After the ODT, the long-range pyrochlore order vanishes but the short-range weberite-type order persists in the long-range disordered defect fluorite structure. Notably, a drop in the thermal conductivity coincides with emergence of the short-range order, instead of the long-range ODT.

Original language	English
Article number	100098
Journal	Advanced Powder Materials
Volume	2
Issue number	2
DOIs	https://doi.org/10.1016/j.apmate.2022.100098
State	Published - Apr 2023

Funding

Jian Luo graduated from Tsinghua University with dual Bachelor's degrees: one in Materials Science and Engineering and another in Electronics and Computer Technology. After receiving his M.S. and Ph.D. degrees from M.I.T., Luo worked in the industry for more than two years with Lucent Technologies Bell Laboratories and OFS/Fitel. In 2003, he joined the Clemson faculty, where he served as an Assistant/Associate/Full Professor of Materials Science and Engineering. In 2013, he moved to University of California, San Diego as a Professor of NanoEngineering and Professor of Materials Science and Engineering. Luo group's current research focuses on interfaces in metals and ceramics, high-entropy and compositionally complex ceramics, ultrafast sintering and other novel ceramic processing technologies, high-temperature nanocrystalline alloys, and advanced materials for batteries and other energy-related applications. Luo received a National Science Foundation CAREER award in 2005 (from the Ceramics program) and an AFOSR Young Investigator award in 2007 (from the Metallic Materials program). He was a Vannevar Bush Faculty Fellow (2014) and a Minerals, Metals & Materials Society (TMS) Brimacombe Medalist (2019). Luo is a Fellow of the American Ceramic Society (2016), a Fellow of the ASM International (2022), and an Academician of the World Academy of Ceramics (2021). The work is supported by the National Science Foundation (NSF) via Grant No. DMR-2026193. A portion of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the ORNL. The STEM work was performed at the Irvine Materials Research Institute (IMRI). The work is supported by the National Science Foundation (NSF) via Grant No. DMR-2026193 . A portion of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the ORNL. The STEM work was performed at the Irvine Materials Research Institute (IMRI).

Keywords

Compositionally complex ceramics
High-entropy ceramics
Neutron diffraction
Neutron total scattering
Order-disorder transition
Short-range order

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10.1016/j.apmate.2022.100098

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title = "Long- and short-range orders in 10-component compositionally complex ceramics",

abstract = "Neutron diffraction and total scattering are combined to investigate a series of single-phase 10-component compositionally complex fluorite-based oxides, [(Pr0.375Nd0.375Yb0.25)2(Ti0.5Hf0.25Zr0.25)2O7]1-x[(DyHoErNb)O7]x, denoted as 10CCFBOxNb. A long-range order-disorder transition (ODT) occurs at x = 0.81 ± 0.01 from the ordered pyrochlore to disordered defect fluorite. In contrast to ternary oxides, this ODT occurs abruptly without an observable two-phase region; moreover, the phase stability in 10CCFBOs deviates from the well-established criteria for simpler oxides. Rietveld refinements of neutron diffraction patterns suggest that this ODT occurs via the migration of oxygen anions from the position 48f to 8a, with a small final jump at the ODT; however, the 8a oxygen occupancy changes gradually (without an observable discontinuous jump). We further discover diffuse scattering in Nb-rich compositions, which suggests the presence of short-range order. Using small-box modelling, four compositions near ODT (x = 0.75, 0.8, 0.85, and 1) can be better fitted by C2221 weberite ordering for the local polyhedral structure at nanoscale. Interestingly, 10CCFBO0.75Nb and 10CCFBO0.8Nb possess both long-range pyrochlore order and short-range weberite-type order, which can be understood from severe local distortion of the pyrochlore polyhedral structure. Thus, weberite-type short-range order emerges before the ODT, coexisting and interacting with long-range pyrochlore order. After the ODT, the long-range pyrochlore order vanishes but the short-range weberite-type order persists in the long-range disordered defect fluorite structure. Notably, a drop in the thermal conductivity coincides with emergence of the short-range order, instead of the long-range ODT.",

keywords = "Compositionally complex ceramics, High-entropy ceramics, Neutron diffraction, Neutron total scattering, Order-disorder transition, Short-range order",

author = "Dawei Zhang and Yan Chen and Heidy Vega and Tianshi Feng and Dunji Yu and Michelle Everett and Joerg Neuefeind and Ke An and Renkun Chen and Jian Luo",

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AU - Zhang, Dawei

AU - Chen, Yan

AU - Vega, Heidy

AU - Feng, Tianshi

AU - Yu, Dunji

AU - Everett, Michelle

AU - Neuefeind, Joerg

AU - An, Ke

AU - Chen, Renkun

AU - Luo, Jian

PY - 2023/4

Y1 - 2023/4

N2 - Neutron diffraction and total scattering are combined to investigate a series of single-phase 10-component compositionally complex fluorite-based oxides, [(Pr0.375Nd0.375Yb0.25)2(Ti0.5Hf0.25Zr0.25)2O7]1-x[(DyHoErNb)O7]x, denoted as 10CCFBOxNb. A long-range order-disorder transition (ODT) occurs at x = 0.81 ± 0.01 from the ordered pyrochlore to disordered defect fluorite. In contrast to ternary oxides, this ODT occurs abruptly without an observable two-phase region; moreover, the phase stability in 10CCFBOs deviates from the well-established criteria for simpler oxides. Rietveld refinements of neutron diffraction patterns suggest that this ODT occurs via the migration of oxygen anions from the position 48f to 8a, with a small final jump at the ODT; however, the 8a oxygen occupancy changes gradually (without an observable discontinuous jump). We further discover diffuse scattering in Nb-rich compositions, which suggests the presence of short-range order. Using small-box modelling, four compositions near ODT (x = 0.75, 0.8, 0.85, and 1) can be better fitted by C2221 weberite ordering for the local polyhedral structure at nanoscale. Interestingly, 10CCFBO0.75Nb and 10CCFBO0.8Nb possess both long-range pyrochlore order and short-range weberite-type order, which can be understood from severe local distortion of the pyrochlore polyhedral structure. Thus, weberite-type short-range order emerges before the ODT, coexisting and interacting with long-range pyrochlore order. After the ODT, the long-range pyrochlore order vanishes but the short-range weberite-type order persists in the long-range disordered defect fluorite structure. Notably, a drop in the thermal conductivity coincides with emergence of the short-range order, instead of the long-range ODT.

AB - Neutron diffraction and total scattering are combined to investigate a series of single-phase 10-component compositionally complex fluorite-based oxides, [(Pr0.375Nd0.375Yb0.25)2(Ti0.5Hf0.25Zr0.25)2O7]1-x[(DyHoErNb)O7]x, denoted as 10CCFBOxNb. A long-range order-disorder transition (ODT) occurs at x = 0.81 ± 0.01 from the ordered pyrochlore to disordered defect fluorite. In contrast to ternary oxides, this ODT occurs abruptly without an observable two-phase region; moreover, the phase stability in 10CCFBOs deviates from the well-established criteria for simpler oxides. Rietveld refinements of neutron diffraction patterns suggest that this ODT occurs via the migration of oxygen anions from the position 48f to 8a, with a small final jump at the ODT; however, the 8a oxygen occupancy changes gradually (without an observable discontinuous jump). We further discover diffuse scattering in Nb-rich compositions, which suggests the presence of short-range order. Using small-box modelling, four compositions near ODT (x = 0.75, 0.8, 0.85, and 1) can be better fitted by C2221 weberite ordering for the local polyhedral structure at nanoscale. Interestingly, 10CCFBO0.75Nb and 10CCFBO0.8Nb possess both long-range pyrochlore order and short-range weberite-type order, which can be understood from severe local distortion of the pyrochlore polyhedral structure. Thus, weberite-type short-range order emerges before the ODT, coexisting and interacting with long-range pyrochlore order. After the ODT, the long-range pyrochlore order vanishes but the short-range weberite-type order persists in the long-range disordered defect fluorite structure. Notably, a drop in the thermal conductivity coincides with emergence of the short-range order, instead of the long-range ODT.

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KW - High-entropy ceramics

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KW - Neutron total scattering

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Long- and short-range orders in 10-component compositionally complex ceramics

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