Browsing by Author "Li, JY"

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    Crystal-liquid duality driven ultralow two-channel thermal conductivity in α-MgAgSb
    (AIP Publishing, 2024-03) Li, JY; Li, XY; Zhang, YS; Zhu, J; Zhao, E; Kofu, M; Nakajima, K; Avdeev, M; Liu, PF; Sui, Jiehe; Zhao, HSZ; Wang, FW; Zhang, JR
    The desire for intrinsically low lattice thermal conductivity (κL) in thermoelectrics motivates numerous efforts on understanding the microscopic mechanisms of heat transport in solids. Here, based on theoretical calculations, we demonstrate that α-MgAgSb hosts low-energy localized phonon bands and avoided crossing of the rattler modes, which coincides with the inelastic neutron scattering result. Using the two-channel lattice dynamical approach, we find, besides the conventional contribution (∼70% at 300 K) from particlelike phonons propagating, the coherence contribution dominated by the wavelike tunneling of phonons accounts for ∼30% of the total κL at 300 K. By considering dual contributions, our calculated room-temperature κL of 0.64 W m−1 K−1 well agrees with the experimental value of 0.63 W m−1 K−1. More importantly, our computations give a nonstandard κL ∝ T−0.61 dependence, perfectly explaining the abnormal temperature-trend of ∼T−0.57 in experiment for α-MgAgSb. By molecular dynamics simulation, we reveal that the structure simultaneously has soft crystalline sublattices with the metavalent bonding and fluctuating liquid-like sublattices with thermally induced large amplitude vibrations. These diverse forms of chemical bonding arouse mixed part-crystal part-liquid state, scatter strongly heat-carrying phonons, and finally produce extremely low κL. The fundamental research from this study will accelerate the design of ultralow-κL materials for energy-conversion applications. © 2024 AIP Publishing LLC
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    A global database of holocene paleotemperature records
    (Springer Nature Limited, 2020-04-14) Kaufman, DS; McKay, N; Rouston, C; Erb, M; Davis, B; Heiri, O; Jaccard, SL; Tierney, J; Dätwyler, C; Axford, Y; Brussel, T; Cartapanis, O; Chase, BM; Dawson, A; de Vernal, A; Engels, S; Jonkers, L; Marsicek, J; Moffa-Sánchez, P; Morrill, C; Oris, A; Rehfeld, K; Saunders, KM; Sommer, PS; Thomas, E; Tonello, M; Tóth, M; Vachula, R; Andreev, A; Bertrand, S; Biskaborn, B; Bringué, M; Brooks, S; Caniupán, M; Chevalier, M; Cwynar, L; Emile-Geay, J; Fegyveresi, J; Feurdean, A; Finsinger, W; Fortin, MC; Foster, L; Fox, M; Gajewski, K; Grosjean, M; Hausmann, S; Heinrichs, M; Holmes, N; Ilyashuk, B; Ilyashuk, E; Juggins, S; Khider, D; Koinig, K; Langdon, P; Larocque-Tobler, I; Li, JY; Lotter, A; Luoto, T; Mackay, A; Magyari, E; Malevich, S; Mark, B; Massaferro, J; Montade, V; Nazarova, L; Novenko, E; Pařil, P; Pearson, E; Peros, M; Peinitz, R; Płóciennik, M; Porinchu, D; Potito, A; Rees, ABH; Reinemann, S; Roberts, SJ; Rolland, N; Salonen, S; Self, A; Seppä, H; Shala, S; St-Jacques, JM; Stenni, B; Syrykh, L; Tarrats, P; Taylor, K; van den Bos, V; Velle, G; Wahl, E; Walker, I; Wilmshurst, J; Zhang, E; Zhilich, S
    A comprehensive database of paleoclimate records is needed to place recent warming into the longer-term context of natural climate variability. We present a global compilation of quality-controlled, published, temperature-sensitive proxy records extending back 12,000 years through the Holocene. Data were compiled from 679 sites where time series cover at least 4000 years, are resolved at sub-millennial scale (median spacing of 400 years or finer) and have at least one age control point every 3000 years, with cut-off values slackened in data-sparse regions. The data derive from lake sediment (51%), marine sediment (31%), peat (11%), glacier ice (3%), and other natural archives. The database contains 1319 records, including 157 from the Southern Hemisphere. The multi-proxy database comprises paleotemperature time series based on ecological assemblages, as well as biophysical and geochemical indicators that reflect mean annual or seasonal temperatures, as encoded in the database. This database can be used to reconstruct the spatiotemporal evolution of Holocene temperature at global to regional scales, and is publicly available in Linked Paleo Data (LiPD) format. © 2020 The Authors
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    Revisiting the cubic crystal structures of Sr4Nb2O9 and Sr5Nb2O10
    (Elsevier, 2021-11-01) Li, JY; Wang, CH; Wang, XM; Avdeev, M; Ling, CD; Kennedy, BJ
    We have synthesized polycrystalline and single crystal samples of Sr4Nb2O9 and Sr5Nb2O10 and revisited the crystal structure of the high-temperature cubic phase. By careful analysis of single-crystal X-ray diffraction (SXRD), powder synchrotron X-ray diffraction (Syn-PXRD) and powder neutron diffraction (PND) data, we arrive at a structure model in space group F4¯3m (#216), a subgroup of the reported Fm3¯m (#225) model. The F4¯3m model gives a better fit to the diffraction data, especially the PND data. We observed an interstitial oxide ion (O3) on the 48h site near the typical perovskite 24e site (O1), which gives a Td Nb–O symmetry rather than an Oh one as found in the Fm3¯m model. The temperature-dependent conductivities of Sr4Nb2O9 and Sr5Nb2O10 in dried O2 were studied using impedance spectroscopy. The activation energies of Sr4Nb2O9 and Sr5Nb2O10 were estimated to be 1.18(1) eV and 1.17(4) eV, respectively. This disordered crystallographic arrangement of the O1 and O3 anions is likely a key structural factor behind oxide ionic migration in Sr4Nb2O9 and Sr5Nb2O10. © 2021 Elsevier Inc.