“Electron-irradiation-facilitated production of chemically homogenized nanotwins in nanolaminated carbides”. Zhang H, Jin Q, Hu T, Liu X, Zhang Z, Hu C, Zhou Y, Han Y, Wang X, Journal of Advanced Ceramics 12, 1288 (2023). http://doi.org/10.26599/JAC.2023.9220757
Abstract: Twin boundaries have been exploited to stabilize ultrafine grains and improve mechanical properties of nanomaterials. The production of the twin boundaries and nanotwins is however prohibitively challenging in carbide ceramics. Using a scanning transmission electron microscope as a unique platform for atomic-scale structure engineering, we demonstrate that twin platelets could be produced in carbides by engineering antisite defects. The antisite defects at metal sites in various layered ternary carbides are collectively and controllably generated, and the metal elements are homogenized by electron irradiation, which transforms a twin-like lamellae into nanotwin platelets. Accompanying chemical homogenization, alpha-Ti3AlC2 transforms to unconventional beta-Ti3AlC2. The chemical homogeneity and the width of the twin platelets can be tuned by dose and energy of bombarding electrons. Chemically homogenized nanotwins can boost hardness by similar to 45%. Our results provide a new way to produce ultrathin (< 5 nm) nanotwin platelets in scientifically and technologically important carbide materials and showcase feasibility of defect engineering by an angstrom-sized electron probe.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 16.9
DOI: 10.26599/JAC.2023.9220757
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“Universal a-cation splitting in LiNbO₃-type structure driven by intrapositional multivalent coupling”. Han Y, Zeng Y, Hendrickx M, Hadermann J, Stephens PW, Zhu C, Grams CP, Hemberger J, Frank C, Li S, Wu MX, Retuerto M, Croft M, Walker D, Yao D-X, Greenblatt M, Li M-R, Journal Of The American Chemical Society 142, 7168 (2020). http://doi.org/10.1021/JACS.0C01814
Abstract: Understanding the electric dipole switching in multiferroic materials requires deep insight of the atomic-scale local structure evolution to reveal the ferroelectric mechanism, which remains unclear and lacks a solid experimental indicator in high-pressure prepared LiNbO3-type polar magnets. Here, we report the discovery of Zn-ion splitting in LiNbO3-type Zn2FeNbO6 established by multiple diffraction techniques. The coexistence of a high-temperature paraelectric-like phase in the polar Zn2FeNbO6 lattice motivated us to revisit other high-pressure prepared LiNbO3-type A(2)BB'O-6 compounds. The A-site atomic splitting (similar to 1.0-1.2 angstrom between the split-atom pair) in B/B'-mixed Zn2FeTaO6 and O/N-mixed ZnTaO2N is verified by both powder X-ray diffraction structural refinements and high angle annular dark field scanning transmission electron microscopy images, but is absent in single-B-site ZnSnO3. Theoretical calculations are in good agreement with experimental results and suggest that this kind of A-site splitting also exists in the B-site mixed Mn-analogues, Mn2FeMO6 (M = Nb, Ta) and anion-mixed MnTaO2N, where the smaller A-site splitting (similar to 0.2 angstrom atomic displacement) is attributed to magnetic interactions and bonding between A and B cations. These findings reveal universal A-site splitting in LiNbO3-type structures with mixed multivalent B/B', or anionic sites, and the splitting-atomic displacement can be strongly suppressed by magnetic interactions and/or hybridization of valence bands between d electrons of the A- and B-site cations.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 15
Times cited: 1
DOI: 10.1021/JACS.0C01814
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