Browsing by Author "Zhou, H"

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    Identifying migration channels and bottlenecks in monoclinic NASICON-type solid electrolytes with hierarchical ion-transport algorithms
    (Wiley, 2021-09-07) Zou, Z; Ma, N; Wang, AP; Ran, YB; Song, T; He, B; Ye, AJ; Mi, PH; Zhang, LW; Zhou, H; Jiao, Y; Liu, JP; Wang, D; Li, YJ; Avdeev, M; Shi, S
    Monoclinic natrium superionic conductors (NASICON; Na3Zr2Si2PO12) are well-known Na-ion solid electrolytes which have been studied for 40 years. However, due to the low symmetry of the crystal structure, identifying the migration channels of monoclinic NASICON accurately still remains unsolved. Here, a cross-verified study of Na+ diffusion pathways in monoclinic NASICON by integrating geometric analysis of channels and bottlenecks, bond-valence energy landscapes analysis, and ab initio molecular dynamics simulations is presented. The diffusion limiting bottlenecks, the anisotropy of conductivity, and the time and temperature dependence of Na+ distribution over the channels are characterized and strategies for improving both bulk and total conductivity of monoclinic NASICON-type solid electrolytes are proposed. This set of hierarchical ion-transport algorithms not only shows the efficiency and practicality in revealing the ion transport behavior in monoclinic NASICON-type materials but also provides guidelines for optimizing their conductive properties that can be readily extended to other solid electrolytes. © 2021 Wiley-VCH GmbH
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    Negative thermal expansion of Ni-doped MnCoGe around room temperature - magnetic tuning
    (Australian Institute of Physics, 2019-02-05) Ren, QY; Hutchinson, WD; Wang, JL; Studer, AJ; Wang, G; Zhou, H; Ma, J; Campbell, SJ
    Several materials have been shown to exhibit abnormal contraction with increasing temperature; the phenomenon of negative thermal expansion (NTE). Given this special property, NTE materials fulfill important functions in many modern technologies, such as electrodes of fuel cell, organic light-emitting diode (OLED), optical fibre, as well as high precision electronics and optical mirrors. In general, Nate properties are associated with local structural distortions or phase transitions, such as transverse phonon vibration in rigid unit modes, exile network of metal-organic framework, charge transfer, magneto-volume effect, ferroelectric transition, as well as displacive phase transition. Control or manipulation of Nate properties have become topics of increasing importance over the past two decades. Effective methods to produce materials with Nate properties include chemical doping, nanostructuralization, hydration and applied pressure. Recently, MoCoGe-based compounds were considered as a group of materials that exhibit giant NTE, with this behaviour attributed to the displacive martensitic phase transformation. In this investigation, we reported a new method to manipulate the NTE properties using applied magnetic fields. It is found that doping of 5% Ni on the Mn site could bring about a magneto-structural (MS) coupling in MnCoGe-based compounds. Magnetic-field-dependent neutron diffraction measurements demonstrated that an 8 T magnetic field could suppress the NTE by 31% at 295 K through this MS coupling.
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    Pressure-modulated magnetism and negative thermal expansion in the Ho2Fe17 intermetallic compound
    (American Chemical Society, 2023-05-25) Cao, YL; Zhou, H; Khmelevskyi, S; Lin, K; Avdeev, M; Wang, CW; Wang, B; Hu, F; Kato,; Hattori, T; Abe, J; Ohara, K; Kawaguchi, S; Li, Q; Fukuda, M; Nishikubo, T; Lee, K; Koike, T; Liu, Q; Miao, J; Deng, JX; Shen, B; Azuma, M; Xing, X
    Hydrostatic and chemical pressure are efficient stimuli to alter the crystal structure and are commonly used for tuning electronic and magnetic properties in materials science. However, chemical pressure is difficult to quantify and a clear correspondence between these two types of pressure is still lacking. Here, we study intermetallic candidates for a permanent magnet with a negative thermal expansion (NTE). Based on in situ synchrotron X-ray diffraction, negative chemical pressure is revealed in Ho2Fe17 on Al doping and quantitatively evaluated by using temperature and pressure dependence of unit cell volume. A combination of magnetization and neutron diffraction measurements also allowed one to compare the effect of chemical pressure on magnetic ordering with that of hydrostatic pressure. Intriguingly, pressure can be used to control suppression and enhancement of NTE. Electronic structure calculations indicate that pressure affected the top of the majority band with respect to the Fermi level (EF), which has implications for the magnetic stability, which in turn plays a critical role in modulating magnetism and NTE. This work presents a good example of understanding the effect of pressure and utilizing it to control properties of functional materials. © 2024 American Chemical Society
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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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    Relationships between Na+ distribution, concerted migration, and diffusion properties in rhombohedral NASICON
    (Wiley, 2020-06-24) Zou, ZY; Ma, N; Wang, AP; Ran, YB; Song, T; Jiao, Y; Zhou, H; Shi, W; He, B; Wang, D; Li, YJ; Avdeev, M; Shi, S
    Rhombohedral NaZr2(PO4)3 is the prototype of all the NASICON-type materials. The ionic diffusion in these rhombohedral NASICON materials is highly influenced by the ionic migration channels and the bottlenecks in the channels which have been extensively studied. However, no consensus is reached as to which one is the preferential ionic migration channel. Moreover, the relationships between the Na+ distribution over the multiple available sites, concerted migration, and diffusion properties remain elusive. Using ab initio molecular dynamics simulations, here it is shown that the Na+ ions tend to migrate through the Na1–Na3–Na2–Na3–Na1 channels rather than through the Na2–Na3–Na3–Na2 channels. There are two types of concerted migration mechanisms: two Na+ ions located at the adjacent Na1 and Na2 sites can migrate either in the same direction or at an angle. Both mechanisms exhibit relatively low migration barriers owing to the potential energy conversion during the Na+ ions migration process. Redistribution of Na+ ions from the most stable Na1 sites to Na2 on increasing Na+ total content further facilitates the concerted migration and promotes the Na+ ion mobility. The work establishes a connection between the Na+ concentration in rhombohedral NASICON materials and their diffusion properties. © 1999-2021 John Wiley & Sons, Inc.