Electronic ionization induced atom migration in spinel MgAl2O4

Jiang, Nan; Spence, John C. H.

doi:10.1016/j.jnucmat.2010.06.013

Cited by 16 publications

(9 citation statements)

References 43 publications

(44 reference statements)

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“…The detailed damage mechanism originating from this induced electric field has been described in recent studies [3,135]. Various damage phenomena, which include gas bubble formation, nanocrystal precipitation, phase transformation and phase decomposition, can be interpreted within the framework of this induced electric field mechanism [78,132,133,[136][137][138][139][140].…”

Section: Induced-electric-field Modelmentioning

confidence: 99%

Electron beam damage in oxides: a review

2015

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This review summarizes a variety of beam damage phenomena relating to oxides in (scanning) transmission electron microscopes, and underlines the shortcomings of currently popular mechanisms. These phenomena include mass loss, valence state reduction, phase decomposition, precipitation, gas bubble formation, phase transformation, amorphization and crystallization. Moreover, beam damage is also dependent on specimen thickness, specimen orientation, beam voltage, beam current density and beam size. This article incorporates all of these damage phenomena and experimental dependences into a general description, interpreted by a unified mechanism of damage by induced electric field. The induced electric field is produced by positive charges, which are generated from excitation and ionization. The distribution of the induced electric fields inside a specimen is beam-illumination- and specimen-shape- dependent, and associated with the experimental dependence of beam damage. Broadly speaking, the mechanism operates differently in two types of material. In type I, damage increases the resistivity of the irradiated materials, and is thus divergent, resulting in phase separation. In type II, damage reduces the resistivity of the irradiated materials, and is thus convergent, resulting in phase transformation. Damage by this mechanism is dependent on electron-beam current density. The two experimental thresholds are current density and irradiation time. The mechanism comes into effect when these thresholds are exceeded, below which the conventional mechanisms of knock-on and radiolysis still dominate.

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Section: Induced-electric-field Modelmentioning

confidence: 99%

Electron beam damage in oxides: a review

2015

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“…The feature of the O K-edge ELNES of spectrum 2 (irradiated Li 4 Ti 5 O 12 ) was similar to the feature of spectrum 4 (β-Li 2 TiO 3 ), which estimated that its oxygen–cation coordination was octahedral. The structural damage of the Li 4 Ti 5 O 12 phase induced by electron irradiation was explained by the formation of a disordered rock-salt phase by Ti-cation mixing at the spinel 16c and 16d sites. ,, The above cation disordered rock-salt phase formation via electron beam irradiation has also been confirmed in other spinel-type oxide materials such as MgAl 2 O 4 , and MgCo 2 O 4 . The oxygen–cation coordination was altered from the tetrahedral form to an octahedral form by the above cation-site mixing; thus, the shape of the O K-edge ELNES of spectrum 2 (irradiated Li 4 Ti 5 O 12 ) clearly showed the formation of a disordered rock-salt phase via electron irradiation.…”

Section: Resultsmentioning

confidence: 81%

Different Oxygen Desorption Durabilities of Lithium Titanium Oxides as Confirmed by Transmission Electron Energy-Loss Spectroscopy Analysis of Li₄Ti₅O₁₂ and β-Li₂TiO₃ Biphase Specimens

Kitta

Tada

2021

ACS Appl. Energy Mater.

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Spinel-type Li4Ti5O12 and monoclinic β-Li2TiO3 phases are well known as typical functional materials in lithium titanium oxide. The former phase is practically applied as a negative electrode material for Li-ion battery systems, while the latter phase is used as a tritium breeder blanket material for thermonuclear reactors; thus, the material stability of these phases is essential for their functions. In this study, we investigate the oxygen desorption durability of oxide materials with different structures and chemical formulas by transmission electron microscopy-based electron energy-loss spectroscopy. To compare the different properties of these two phases, biphase specimens that consisted of Li4Ti5O12 and β-Li2TiO3 phases with a homogeneous thickness were successfully prepared by a two-step thermal process to perform suitable analysis by transmission electron microscopy. Irradiation with a scanning transmission electron microscopy probe, followed by electron energy-loss spectroscopy analysis, was performed in the Li4Ti5O12/β-Li2TiO3 interphase region of the biphase specimen, revealing that the oxygen desorption feature of β-Li2TiO3 was approximately one-third that of the Li4Ti5O12 phase. The stability of the cation–oxygen bond in each oxide crystal was also simulated by reaction enthalpy analysis based on density functional theory calculations, and the lattice stability of the Li4Ti5O12 phase was estimated to be three times higher than that of the β-Li2TiO3 phase. The oxygen vacancy formation energy of the β-Li2TiO3 lattice was approximately 0.8 eV higher than that of the Li4Ti5O12 phase. Thus, the reason for the different oxygen desorption durabilities of these oxide phases is not the stability of the cation–oxygen bond but the ease of reduction phase formation via oxygen desorption.

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“…Based on the statistical results, it can be clearly noted that the phase-transition speed is almost linear to the electron dose rate. As reported in the radiolysis process, the transformation or diffusion rate is in proportion to the current density of the incident electron beam, , which is consistent with our results. In addition, it is of interest to find that there is a latent time for the phase transition of LTO under electron beam irradiation, which could be related to radiolysis that needs a latent time to store enough internal energy through the inelastic electron momentum transfer .…”

Section: Resultsmentioning

confidence: 99%

Revealing the Phase-Transition Dynamics and Mechanism in a Spinel Li₄Ti₅O₁₂ Anode Material through in Situ Electron Microscopy

Wang

Zhi

Cheng

et al. 2020

ACS Appl. Mater. Interfaces

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Spinel Li4Ti5O12 is considered as a promising anode material for long-life lithium-ion batteries because of the negligible volumetric variation during the insertion and extraction of Li ions. Phase transition is an inevitable process during the migration of Li ions, and the transition process and mechanism need detailed investigation down to the atomic scale. In this study, we investigated the behavior and mechanism on the phase transition of Li4Ti5O12 through in situ transmission electron microscopy (TEM). It has been found that the spinel-structured Li4Ti5O12 was gradually transformed to a rock salt structure under electron beam irradiation. A sharp interface with an epitaxial relationship was observed between the transformed rock salt phase and the parent spinel phase. Furthermore, the heterostructure with different crystal structures of Li4Ti5O12 has been precisely tailored with electron beam irradiation. Our detailed in situ TEM results and theoretical calculations led to unprecedented level on the understanding of phase-transition mechanism in Li4Ti5O12. This study demonstrates a possible approach to precisely engineer the crystal structure of materials and to realize a well-designed heterostructure in electrode materials.

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Electronic ionization induced atom migration in spinel MgAl2O4

Cited by 16 publications

References 43 publications

Electron beam damage in oxides: a review

Electron beam damage in oxides: a review

Different Oxygen Desorption Durabilities of Lithium Titanium Oxides as Confirmed by Transmission Electron Energy-Loss Spectroscopy Analysis of Li₄Ti₅O₁₂ and β-Li₂TiO₃ Biphase Specimens

Revealing the Phase-Transition Dynamics and Mechanism in a Spinel Li₄Ti₅O₁₂ Anode Material through in Situ Electron Microscopy

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Electronic ionization induced atom migration in spinel MgAl2O4

Cited by 16 publications

References 43 publications

Electron beam damage in oxides: a review

Electron beam damage in oxides: a review

Different Oxygen Desorption Durabilities of Lithium Titanium Oxides as Confirmed by Transmission Electron Energy-Loss Spectroscopy Analysis of Li4Ti5O12 and β-Li2TiO3 Biphase Specimens

Revealing the Phase-Transition Dynamics and Mechanism in a Spinel Li4Ti5O12 Anode Material through in Situ Electron Microscopy

Contact Info

Product

Resources

About

Different Oxygen Desorption Durabilities of Lithium Titanium Oxides as Confirmed by Transmission Electron Energy-Loss Spectroscopy Analysis of Li₄Ti₅O₁₂ and β-Li₂TiO₃ Biphase Specimens

Revealing the Phase-Transition Dynamics and Mechanism in a Spinel Li₄Ti₅O₁₂ Anode Material through in Situ Electron Microscopy