Browsing by Author "Yu, D"
Now showing 1 - 5 of 5
Results Per Page
Sort Options
- ItemA colossal barocaloric effect induced by the creation of a high-pressure phase(Royal Society of Chemistry (RSC), 2023-01-13) Zhang, Z; Jiang, X; Hattori, T; Xu, X; Li, M; Yu, CY; Zhang, Z; Yu, D; Mole, RA; Yano, SI; Chen, J; He, LH; Wang, CW; Wang, H; Li, B; Zhang, ZDAs a promising environment-friendly alternative to current vapor-compression refrigeration, solid-state refrigeration based on the barocaloric effect has been attracting worldwide attention. Generally, both phases in which a barocaloric effect occurs are present at ambient pressure. Here, instead, we demonstrate that KPF6 exhibits a colossal barocaloric effect due to the creation of a high-pressure rhombohedral phase. The phase diagram is constructed based on pressure-dependent calorimetric, Raman scattering, and neutron diffraction measurements. The present study is expected to provide an alternative routine to colossal barocaloric effects through the creation of a high-pressure phase. © Royal Society of Chemistry 2024.
- ItemLead-free (Ag,K)NbO3materials for high-performance explosive energy conversion(Australian Institute of Nuclear Science and Engineering (AINSE), 2020-11-11) Liu, Z; Lu, T; Xue, F; Withers, RL; Studer, AJ; Narayanan, N; Dong, XL; Yu, D; Chen, L; Wang, G; Liu, YExplosive energy conversion materials with extremely rapid response times have a diverse and growing range of applications in energy, medical, and mining areas. Research into the underlying mechanisms and the search for new candidate materials is so limited that Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 is still the dominant material after half a century. In this work, we report the discovery of a new, lead-free ferroelectric material, (Ag0.935K0.065)NbO3 for explosive energy conversion applications. This material not only possesses a record-high energy storage density of 5.401 J/g, but also exhibits excellent temperature stability (up to a disruptive ferroelectric to ferroelectric phase transition at 150oC) by comparison with Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 (which exhibits the ferroelectric to ferroelectric phase transition but at the much lower temperature of 41~70oC). (Ag0.935K0.065)NbO3 enables extremely high power, energy conversion within 1.8 microseconds, generating a pulse with e.g. a current ~ 22 A. Furthermore, pressure-dependent physical characterization, together with transmission electron microscopy, in-situ neutron diffraction analysis and theoretical modelling, reveals the mechanism underlying the observed explosive energy conversion behavior. It is found that the fast release of the stored energy can be attributed to a pressure-induced octahedral tilt change from a-a-c+ to AgNbO3-type a-a-c-/a-a-c+, in accordance with an irreversible pressure driven FE-AFE phase transition. This work provides not only an alternative (with significantly better performance) to the current commercially-employed lead-containing materials, but also provides guidance for the further development of new materials and devices for explosive energy conversion applications. Copyright © 2020 The Authors.
- ItemLiquid-like ionic diffusion in solid bismuth oxide revealed by coherent quasielastic neutron scattering(American Chemical Society (ACS), 2017-08-07) Wind, J; Mole, RA; Yu, D; Ling, CDThe exceptional oxide ionic conductivity of the high-temperature phase of bismuth oxide gives rise to a characteristic "quasielastic" broadening of its neutron scattering spectrum. We show that the oscillating form of this broadening can be fit using a modified version of a jump-diffusion model previously reserved for liquid ionic conductors. Fit parameters include a quantitative jump distance and a semiquantitative diffusion coefficient. In the case presented here, the results show that diffusion is isotropic (liquid-like) even though some directions present shorter oxygen-vacancy distances, an insight corroborated by computational dynamics simulations. More broadly, the results show for the first time that quasielastic neutron scattering can be directly analyzed to yield quantitative insights into the atomic-scale mechanisms of solid-state ionic conduction, even when the diffusing species is a coherent neutron scatterer such as oxygen. This shows its power as a tool for studying functional solid-state materials, notably for solid-oxide fuel cells and, potentially, lithium-ion batteries. © 2017 American Chemical Society.
- ItemRole of a-site molecular ions in the polar functionality of metal–organic framework perovskites(American Chemical Society (ACS), 2021-12-28) Lu, T; Cortie, DL; Li, ZX; Narayanan, N; Liu, Z; Sun, QB; Frankcombe, TJ; McIntyre, GJ; Yu, D; Liu, YRecent studies on organic–inorganic hybrid perovskites (OIHPs) and ferroelectric metal–organic framework perovskites (MOFPs) reveal their superb performance as highly efficient materials for photovoltaics and ferroelectrics. This has enabled the development of a new generation of optic-electronic-mechanical devices based on green chemistry. However, the fundamental understanding of these polarization-related functionalities is not yet clear, which has hindered the progress in further designing and developing materials with expected properties. In this work, we investigate three MOFPs that have the same Mg(HCOO)3– frameworks with different molecular ions: [CH3NH3][Mg(HCOO)3] (MA-MOF), [(CH3)2NH2][Mg(HCOO)3] (DMA-MOF), and [C(NH2)3][Mg(HCOO)3] (GUA-MOF). Single-crystal and powder X-ray diffraction, inelastic neutron spectroscopy, and ab initio molecular dynamics simulations are combined to achieve a detailed description of the three MOFPs’ static and dynamic structures as a function of temperature. Intriguingly, our study reveals that the alignments and motions of the guest molecular ions are highly dependent on the directional hydrogen bonds that link N–H units to the surrounding MgO6 octahedra through the O acceptor from the frameworks. At the same time, the size, dynamic behavior, and alignments of the A-site molecular ions influence the distortive framework structures and their temperature-dependent deformation. Therefore, the mutual interaction between the guest and the framework determines the overall functionalities of the MOFPs. This study indicates that the configuration of the A-site molecular ions and the potential hydrogen bonds are critical to design the polar functionalities in both MOFPs and OIHPs. © 2021 American Chemical Society
- ItemTwo-dimensional quantum universality in the spin-1/2 triangular-lattice quantum antiferromagnet Na2BaCo(PO4)2(Proceedings of the National Academy of Sciences, 2022-12-15) Sheng, JM; Wang, L; Candini, A; Jiang, W; Huang, L; Xi, B; Zhao, J; Ge, H; Zhao, N; Fu, Y; Ren, J; Yang, J; Miao, P; Tong, X; Yu, D; Wang, S; Liu, Q; Kofu, M; Mole, RA; Biasiol, G; Yu, DH; Zaliznyak, IA; Mei, JW; Wu, LAn interplay of geometrical frustration and strong quantum fluctuations in a spin-1/2 triangular-lattice antiferromagnet (TAF) can lead to exotic quantum states. Here, we report the neutron-scattering, magnetization, specific heat, and magnetocaloric studies of the recently discovered spin-1/2 TAF Na2BaCo(PO4)2, which can be described by a spin-1/2 easy axis XXZ model. The zero-field neutron diffraction experiment reveals an incommensurate antiferromagnetic ground state with a significantly reduced ordered moment of about 0.54(2) μB/Co. Different magnetic phase diagrams with magnetic fields in the ab plane and along the easy c-axis were extracted based on the magnetic susceptibility, specific heat, and elastic neutron-scattering results. In addition, two-dimensional (2D) spin dispersion in the triangular plane was observed in the high-field polarized state, and microscopic exchange parameters of the spin Hamiltonian have been determined through the linear spin wave theory. Consistently, quantum critical behaviors with the universality class of d = 2 and νz = 1 were established in the vicinity of the saturation field, where a Bose–Einstein condensation (BEC) of diluted magnons occurs. The newly discovered quantum criticality and fractional magnetization phase in this ideal spin-1/2 TAF present exciting opportunities for exploring exotic quantum phenomena. © 2022 the Author(s). Published by PNAS. This article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).