Tracer diffusion in proton-exchanged congruent LiNbO<sub>3</sub> crystals as a function of hydrogen content

Dörrer, Lars; Heller, R.; Schmidt, Harald

doi:10.1039/d2cp01818g

Cited by 5 publications

(6 citation statements)

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“…It is noteworthy that the ions' diffusion coefficients are much larger than those inside the crystal. The latter are of 24,25 ∼10 −14 ÷ 10 −16 m 2 s −1 magnitude order. Our estimations confirm fundamental differences in the diffusion properties of ions in liquids and in solids.…”

Section: ■ Numerical Proceduresmentioning

confidence: 90%

Dynamics of the Proton Exchange Process in Benzoic Acid Interacting with Lithium Niobate Crystals

et al. 2023

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This paper provides a numerical analysis of the behavior of the ion boundary layer formed during proton exchange. Thermal dissociation of benzoic acid melt molecules leads to the formation of benzoate ions and hydrogen ions. The latter can be absorbed by a lithium niobate wafer, with subsequent diffusion of lithium ions in the acid. The mathematical model proposed in the article implies that it is possible to use continuous media approximation to describe this phenomenon. The statement of the current problem includes both diffusion and electrostatic mechanisms of mass transfer and the recombination mechanism of ion interaction. The numerical scheme, based on a two-field method, has shown a steady-state formation, characterized by exponential-like profiles of concentration in the presence of an induced nonuniform electric field. It is important to note that the net charge of the system remains zero. The results of numerical simulation have demonstrated the formation of a boundary layer of benzoate ions. At the same time, nonuniformities that appear in the layer do not create instability that breaks mechanical equilibrium, and they do not lead to a high-scale concentration convection.

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Section: ■ Numerical Proceduresmentioning

confidence: 90%

Dynamics of the Proton Exchange Process in Benzoic Acid Interacting with Lithium Niobate Crystals

et al. 2023

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“…In the case of LiNbO 3 single crystals, proton exchange resulted in micrometric-thick surface layers where Li is substituted by hydrogen. The Li diffusivity was measured to increase by many orders of magnitude when the H content is increased [142]. Thus, cycling of partially proton-exchanged amorphous LiNbO 3 may further boost Li kinetics.…”

Section: Remarks Open Questions and Outlookmentioning

confidence: 98%

“…The proton-exchange process can be carried out in a mixture of benzoic acid and lithium benzoate. During proton exchange, lithium is replaced by hydrogen and Li 1−x H x NbO 3 is formed, with x up to 0.85 [142]. In the case of LiNbO 3 single crystals, proton exchange resulted in micrometric-thick surface layers where Li is substituted by hydrogen.…”

Section: Remarks Open Questions and Outlookmentioning

confidence: 99%

Lithium Niobate for Fast Cycling in Li-ion Batteries: Review and New Experimental Results

et al. 2023

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Li-Nb-O-based insertion layers between electrodes and electrolytes of Li-ion batteries (LIBs) are known to protect the electrodes and electrolytes from unwanted reactions and to enhance Li transport across interfaces. An improved operation of LIBs, including all-solid-state LIBs, is reached with Li-Nb-O-based insertion layers. This work reviews the suitability of polymorphic Li-Nb-O-based compounds (e.g., crystalline, amorphous, and mesoporous bulk materials and films produced by various methodologies) for LIB operation. The literature survey on the benefits of niobium-oxide-based materials for LIBs, and additional experimental results obtained from neutron scattering and electrochemical experiments on amorphous LiNbO3 films are the focus of the present work. Neutron reflectometry reveals a higher porosity in ion-beam sputtered amorphous LiNbO3 films (22% free volume) than in other metal oxide films such as amorphous LiAlO2 (8% free volume). The higher porosity explains the higher Li diffusivity reported in the literature for amorphous LiNbO3 films compared to other similar Li-metal oxides. The higher porosity is interpreted to be the reason for the better suitability of LiNbO3 compared to other metal oxides for improved LIB operation. New results are presented on gravimetric and volumetric capacity, potential-resolved Li+ uptake and release, pseudo-capacitive fractions, and Li diffusivities determined electrochemically during long-term cycling of LiNbO3 film electrodes with thicknesses between 14 and 150 nm. The films allow long-term cycling even for fast cycling with rates of 240C possessing reversible capacities as high as 600 mAhg−1. Electrochemical impedance spectroscopy (EIS) shows that the film atomic network is stable during cycling. The Li diffusivity estimated from the rate capability experiments is considerably lower than that obtained by EIS but coincides with that from secondary ion mass spectrometry. The mostly pseudo-capacitive behavior of the LiNbO3 films explains their ability of fast cycling. The results anticipate that amorphous LiNbO3 layers also contribute to the capacity of positive (LiNixMnyCozO2, NMC) and negative LIB electrode materials such as carbon and silicon. As an outlook, in addition to surface-engineering, the bulk-engineering of LIB electrodes may be possible with amorphous and porous LiNbO3 for fast cycling with high reversible capacity.

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“…In LiNbO 3 and related materials, hydrogen is present in low amounts in most of the as-grown crystals as an impurity that may profoundly influence the optical and electronic properties. , The concentration of hydrogen in the as-grown state is difficult to determine, but values on the order of 10 18 −10 19 cm –3 , were reported, depending on the growth atmosphere . High amounts of hydrogen can be incorporated by proton exchange, − where lithium is replaced by hydrogen and a layer of Li 1– x H x NbO 3 is formed at the crystal surface (up to x = 0.85) . This procedure changes the optical refractive index in the exchanged regions reducing optical damage and allows us to produce waveguides. , …”

Section: Introductionmentioning

confidence: 99%

Hydrogen Diffusion in Li(Nb,Ta)O₃ Single Crystals Probed by Infrared Spectroscopy and Secondary Ion Mass Spectrometry

Kofahl,

Dörrer,

Wulfmeier

et al. 2024

Chem. Mater.

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Hydrogen is an impurity that is incorporated into LiNb 1−x Ta x O 3 crystals during crystal growth or during thermal treatment in a humid atmosphere and may influence the physical properties in different ways. In this context, diffusion of hydrogen is an important process because it may enhance the ion conductivity of the material. We investigated the diffusion of hydrogen in LiNbO 3 , LiTaO 3 , and LiNb 0.15 Ta 0.85 O 3 single crystals in the temperature range between 311 and 606 °C using deuterium from a gaseous D 2 O source as a tracer. Diffusivities were determined by analyzing the relative deuterium fraction in the crystal with infrared spectroscopy or secondary ion mass spectrometry. The results are in good agreement with each other. The diffusivities in LiNbO 3 can be described by the Arrhenius law with an activation energy of 0.98 eV. The diffusivities in LiTaO 3 and LiNb 0.15 Ta 0.85 O 3 are nearly identical to those in LiNbO 3 within a maximum factor of 2. A direct interstitial diffusion mechanism is suggested where hydrogen migrates in the energy landscape of the crystal. From a comparison of the partial H and Li ion conductivities calculated from diffusivities to electrical conductivities measured by impedance spectroscopy, we conclude that hydrogen may contribute to the overall conductivity below 400 °C.

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Tracer diffusion in proton-exchanged congruent LiNbO₃ crystals as a function of hydrogen content

Abstract: The proton-exchange process is an effective method of fabricating low-loss waveguides based on LiNbO3 crystals. During proton-exchange, lithium is replaced by hydrogen and Li1-xHxNbO3 is formed. Currently, mechanisms and kinetics...

Cited by 5 publications

References 45 publications

Dynamics of the Proton Exchange Process in Benzoic Acid Interacting with Lithium Niobate Crystals

Dynamics of the Proton Exchange Process in Benzoic Acid Interacting with Lithium Niobate Crystals

Lithium Niobate for Fast Cycling in Li-ion Batteries: Review and New Experimental Results

Hydrogen Diffusion in Li(Nb,Ta)O₃ Single Crystals Probed by Infrared Spectroscopy and Secondary Ion Mass Spectrometry

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Tracer diffusion in proton-exchanged congruent LiNbO3 crystals as a function of hydrogen content

Abstract: The proton-exchange process is an effective method of fabricating low-loss waveguides based on LiNbO3 crystals. During proton-exchange, lithium is replaced by hydrogen and Li1-xHxNbO3 is formed. Currently, mechanisms and kinetics...

Cited by 5 publications

References 45 publications

Dynamics of the Proton Exchange Process in Benzoic Acid Interacting with Lithium Niobate Crystals

Dynamics of the Proton Exchange Process in Benzoic Acid Interacting with Lithium Niobate Crystals

Lithium Niobate for Fast Cycling in Li-ion Batteries: Review and New Experimental Results

Hydrogen Diffusion in Li(Nb,Ta)O3 Single Crystals Probed by Infrared Spectroscopy and Secondary Ion Mass Spectrometry

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Tracer diffusion in proton-exchanged congruent LiNbO₃ crystals as a function of hydrogen content

Hydrogen Diffusion in Li(Nb,Ta)O₃ Single Crystals Probed by Infrared Spectroscopy and Secondary Ion Mass Spectrometry