Spatial distribution of optical coloration in single crystalline LiNbO3 after high-temperature H2/air treatments

Sugak, D.; Syvorotka, I.I.; Buryy, Oleh; Yakhnevych, U.; Solskii, I.; Martynyuk, N.; Suhak, Yuriy; Suchocki, A.; Zhydachevskii, Ya.; Jakieła, R.; Ubizskii, S.; Singh, Ghanshyam; Janyani, Vijay

doi:10.1016/j.optmat.2017.05.022

Cited by 13 publications

(5 citation statements)

References 33 publications

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“…Some additional structure observed near 350 nm and 670 nm in samples having an oxidizing step in their history might be attributed to absorption related to the LiNb 3 O 8 phase. As shown by Sugak et al [36] the coloration is formed near the crystal surface and its distribution depends on annealing temperature. Annealing is assumed to attack the exposed surface of the particles without essentially changing their deeper structure.…”

Section: Discussion Of the Mechanochemical Reaction Including Redox Pmentioning

confidence: 86%

Mechanochemical Reactions of Lithium Niobate Induced by High-Energy Ball-Milling

et al. 2019

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Lithium niobate (LiNbO3, LN) nanocrystals were prepared by ball-milling of the crucible residue of a Czochralski grown congruent single crystal, using a Spex 8000 Mixer Mill with different types of vials (stainless steel, alumina, tungsten carbide) and various milling parameters. Dynamic light scattering and powder X-ray diffraction were used to determine the achieved particle and grain sizes, respectively. Possible contamination from the vials was checked by energy-dispersive X-ray spectroscopy measurements. Milling resulted in sample darkening due to mechanochemical reduction of Nb (V) via polaron and bipolaron formation, oxygen release and Li2O segregation, while subsequent oxidizing heat-treatments recovered the white color with the evaporation of Li2O and crystallization of a LiNb3O8 phase instead. The phase transformations occurring during both the grinding and the post-grinding heat treatments were studied by Raman spectroscopy, X-ray diffraction and optical reflection measurement, while the Li2O content of the as-ground samples was quantitatively measured by coulometric titration.

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Section: Discussion Of the Mechanochemical Reaction Including Redox Pmentioning

confidence: 86%

Mechanochemical Reactions of Lithium Niobate Induced by High-Energy Ball-Milling

et al. 2019

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“…And since the same significant changes in no, ne, Δn were obtained for the undoped sample LN-P2, the only reason for this can only be high-temperature annealing. Surprisingly, none of the works that studied the effect of high-temperature annealing on the optical properties of LiNbO3 [34][35][36][37][38][39][40][41] contain data on the values of the main optical constants of annealed LiNbO3 crystalline samples. It seems that the authors of these works apriority consider such changes impossible.…”

Section: Tablementioning

confidence: 99%

“…In addition, we had the opportunity to study LiNbO3 crystals subjected to hightemperature annealing. As is known, various atmospheres are used for the reduction annealing of LiNbO3 crystals: pure hydrogen [34,35], argon [36,37], various gas mixtures, for example, 90% N2 and 10% H2 [38], 95% Ar and 5% H2 [39] and annealing in vacuum [33, 40 and 41]. Therefore, we hoped that in this case it would be possible to compare the results obtained.…”

Section: Introductionmentioning

confidence: 99%

The Combined Ellipsometric Method of Complete Optical Characterization of Crystals. Iv. Application to Uniaxial Crystal.

Belyukh¹,

Pavlyk²

2022

ELIT

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In the fourth part of the article, the application of the proposed method for the complete optical characterization of crystals to optically uniaxial crystals is considered. The object of the study was lithium niobate (LiNbO3) crystals. Refining the orientation of the optical indicatrix in the samples under study, we confirmed the conclusion by direct measurements that for the implementation of the proposed combined ellipsometric method, knowledge of the crystallographic orientation of the crystal under study is completely optional. The obtained values of the optical constants of the undoped LiNbO3 crystal [no = 2.280(±0.003), ne = 2.202(±0.002), Δn = -0.0775(±0.0015)] fully confirmed the correctness of the proposed method and its efficiency in the investigation of uniaxial crystals. The sensitivity of the combined ellipsometric method was tested on LiNbO3 crystals subjected to high-temperature annealing in an H2O atmosphere. The optical constants obtained for an undoped LiNbO3 crystal [no = 2.2455(±0.0015), ne = 2.1965(±0.0015), Δn = -0.049(±0.001)] and a magnesium-doped LiNbO3 crystal [no = 2.2445(±0.0015), ne = 2.1756(±0.0007), Δn = -0.069(±0.001)] is significantly less than the optical constants of the as grown crystal. It is assumed that the main reason that caused such significant changes is hightemperature annealing in an H2O atmosphere. Our main goal was to show the applicability of the method to the analysis of possible changes in the optical constants of a crystal caused by the influence of various factors on its properties. The results obtained show that the goal has been achieved.

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“…Due to the absence of trapped-hole centers in reduced crystals, a thermodynamical equilibrium is established between antisite-trapped polarons and bipolarons, as observed in the range 122-575 K [36]. For higher temperatures, both kinds are liberated step by step from their bondage, leading to the appearance of free Nb 4+ Nb polarons absorbing near 1 eV [20,43,44]. The underlying kinetics have been observed and modeled in great detail in the whole temperature range, yielding activation energies in full agreement with photoexcitation, DC conductivity, and thermopower experiments [35].…”

Section: Defect Generation In Cln By Thermal Reductionmentioning

confidence: 99%

‘Horror Vacui’ in the Oxygen Sublattice of Lithium Niobate Made Affordable by Cationic Flexibility

Corradi

Kovács

2021

Crystals

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The present review is intended to interest a broader audience interested in the resolution of the several decades-long controversy on the possible role of oxygen-vacancy defects in LiNbO3. Confronting ideas of a selected series of papers from classical experiments to brand new large-scale calculations, a unified interpretation of the defect generation and annealing mechanisms governing processes during thermo- and mechanochemical treatments and irradiations of various types is presented. The dominant role of as-grown and freshly generated Nb antisite defects as traps for small polarons and bipolarons is demonstrated, while mobile lithium vacancies, also acting as hole traps, are shown to provide flexible charge compensation needed for stability. The close relationship between LiNbO3 and the Li battery materials LiNb3O8 and Li3NbO4 is pointed out. The oxygen sublattice of the bulk plays a much more passive role, whereas oxygen loss and Li2O segregation take place in external or internal surface layers of a few nanometers.

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Spatial distribution of optical coloration in single crystalline LiNbO3 after high-temperature H2/air treatments

Cited by 13 publications

References 33 publications

Mechanochemical Reactions of Lithium Niobate Induced by High-Energy Ball-Milling

Mechanochemical Reactions of Lithium Niobate Induced by High-Energy Ball-Milling

The Combined Ellipsometric Method of Complete Optical Characterization of Crystals. Iv. Application to Uniaxial Crystal.

‘Horror Vacui’ in the Oxygen Sublattice of Lithium Niobate Made Affordable by Cationic Flexibility

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