Browsing by Author "Huang, QZ"

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    Quantified zero thermal expansion in magnetic R2Fe17-based intermetallic compounds (R = rare earth)
    (American Chemical Society, 2023-06-13) Cao, YL; Matsukawa, T; Gibbs, A; Avdeev, M; Wang, CW; Wu, H; Huang, QZ; Ohoyama, K; Ishigaki, T; Zhou, H; Li, Q; Miao, J; Lin, K; Xing, XR
    Zero thermal expansion (ZTE) has been a fascinating task for the past few decades due to its great scientific and practical merits. To realize ZTE, negative thermal expansion is typically employed by chemical substitutions on tuning structure features, which often relies on trial and error. Here, we report on exploring quantification of thermal expansion with magnetic ordering in an intermetallic class of R2Fe17 (R = rare earth), which can accurately determine the ZTE composition using a documented database. It demonstrates that the magnetic ordering of the Fe-sublattice contributes to the thermal expansion anomaly through simultaneous examinations of magnetization and neutron powder diffraction. Alternative elements can be manipulated on a Fe-sublattice to control both the total ordered magnetic moments of the Fe-sublattice and Curie temperature, which tailors the temperature variation of the magnetic contributions on thermal expansion. The current work might point to a future for ZTE high throughput searches, anticipated to benefit applications. © 2023 American Chemical Society
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    Substitution-induced structure evolution and Zn2+/Ga3+ ordering in “114” oxides MAZn2Ga2O7 (M = Ca2+, Sr2+; A = Sr2+, Ba2+)
    (American Chemical Society, 2018-06-08) Jiang, PF; Huang, QZ; Avdeev, M; Tao, FQ; Zhou, LJ; Gao, WL; Cong, RH; Yang, T
    The “114” oxides LnBa(Co/Fe)4O7+δ represent a new family of materials that exhibits intriguing physical properties, including geometrically frustrated magnetism, oxygen storage, and magnetoelectric couplings. Various chemical substitutions have been conducted to modify their crystal and magnetic structures as well as physical properties. However, the principles beneath the substitution-induced structural evolution and charge/cationic ordering have not yet been understood. Thus, in this contribution, two complete solid solutions of MAZn2Ga2O7 (M = Ca2+, Sr2+; A = Sr2+, Ba2+) were designed, synthesized, and characterized by Rietveld refinements based on high-resolution X-ray diffraction (XRD) and neutron diffraction (ND) data. The structure symmetry of MAZn2Ga2O7 is determined by the cationic size mismatch between M and A cations that can be defined by the tolerance factor t, i.e., symmetry transitions from P63mc (t > 0.87) to P31c (0.87 > t > 0.75) and to Pna21 (t < 0.75) were observed for MAZn2Ga2O7, associated with the rotation of T1O4 tetrahedra in the triangular layers. The Zn2+/Ga3+ ordering at T sites is also a consequence of the increase or decrease of the average sizes of M and A cations. A small concentration of interstitial oxygen ions can be obtained in Sr2Zn2–xGa2+xO7+x/2 (x = 0.1, 0.2); however, no oxygen ionic conduction was observed at high temperatures, indicating the migration ability of the interstitial oxygen was very limited. © 2018 American Chemical Society
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    Ultrawide temperature range super-invar behavior of R2(Fe, Co)17 materials (R = rare earth)
    (American Physical Society, 2021-07-30) Cao, YL; Lin, KM; Khmelevskyi, S; Avdeev, M; Taddei, KM; Zhang, Q; Huang, QZ; Li, Q; Kato, K; Tang, CC; Gibbs, A; Wang, CW; Deng, JX; Chen, J; Zhang, HJ; Xing, XR
    Super Invar (SIV), i.e., zero thermal expansion of metallic materials underpinned by magnetic ordering, is of great practical merit for a wide range of high precision engineering. However, the relatively narrow temperature window of SIV in most materials restricts its potential applications in many critical fields. Here, we demonstrate the controlled design of thermal expansion in a family of R2(Fe,Co)17 materials (R=rare Earth). We find that adjusting the Fe-Co content tunes the thermal expansion behavior and its optimization leads to a record-wide SIV with good cyclic stability from 3–461 K, almost twice the range of currently known SIV. In situ neutron diffraction, Mössbauer spectra and first-principles calculations reveal the 3d bonding state transition of the Fe-sublattice favors extra lattice stress upon magnetic ordering. On the other hand, Co content induces a dramatic enhancement of the internal molecular field, which can be manipulated to achieve “ultrawide” SIV over broad temperature, composition and magnetic field windows. These findings pave the way for exploiting thermal-expansion-control engineering and related functional materials. © 2021 American Physical Society
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    Unprecedented lattice volume expansion on doping stereochemically active Pb2+ into uniaxially strained structure of CaBa1−xPbxZn2Ga2O7
    (Springer Nature, 2020-03-11) Jiang, PF; Neuefeind, JC; Avdeev, M; Huang, QZ; Yue, MF; Yang, XY; Cong, RH; Yang, T
    Lone pair cations like Pb2+ are extensively utilized to modify and tune physical properties, such as nonlinear optical property and ferroelectricity, of some specific structures owing to their preference to adopt a local distorted coordination environment. Here we report that the incorporation of Pb2+ into the polar “114”-type structure of CaBaZn2Ga2O7 leads to an unexpected cell volume expansion of CaBa1-xPbxZn2Ga2O7 (0 ≤ x ≤ 1), which is a unique structural phenomenon in solid state chemistry. Structure refinements against neutron diffraction and total scattering data and theoretical calculations demonstrate that the unusual evolution of the unit cell for CaBa1-xPbxZn2Ga2O7 is due to the combination of the high stereochemical activity of Pb2+ with the extremely strained [Zn2Ga2O7]4− framework along the c-axis. The unprecedented cell volume expansion of the CaBa1−xPbxZn2Ga2O7 solid solution in fact is a macroscopic performance of the release of uniaxial strain along c-axis when Ba2+ is replaced with smaller Pb2+. This article is licensed under a Creative Commons Attribution 4.0 International License.