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M N Palatnikov - One of the best experts on this subject based on the ideXlab platform.
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Optical Anomalies in LiNbO 3 :Mg Crystals
Optics and Spectroscopy, 2019Co-Authors: N V Sidorov, L. A. Bobreva, M N Palatnikov, N. A. Teplyakova, O. V. MakarovaAbstract:We have observed that LiNbO3:Mg (0.19–5.91 mol % MgO) crystals experience rearrangements in their defect structure with increasing Concentration of Mg and exhibit optical anomalies related with them, which have a Threshold character. We have shown that, at Mg Concentrations close to the first Concentration Threshold at ~3.0 mol % MgO, the optical homogeneity of the crystals increases. When the Mg Concentration approaches the second Concentration Threshold, we have revealed a significant shift (by ~50 cm–1 compared to that in other crystals) of the entire IR absorption spectrum in the range of stretching vibrations of OH groups to the high-frequency range, a sharp decrease in the number of protons, and a jumpwise shift of the absorption edge in the short-wavelength range. We have shown that the shift occurs because all NbLi point defects are replaced by Mg cations near the Concentration Threshold at 5.5 mol % MgO, and, subsequently, Mg cations occupy only positions of Li and Nb cations of an ideal stoichiometric structure, forming MgLi and MgNb point defects.
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Complex Defects in Mg-Doped Lithium Niobate Crystals Over a Wide Concentration Range and Their Manifestation in IR Absorption Spectra in the OH Stretching Vibration Region
Journal of Applied Spectroscopy, 2019Co-Authors: N V Sidorov, L. A. Bobreva, M N PalatnikovAbstract:Structural defects of nominally pure congruent and stoichiometric LiNbO_3 crystals and a series of congruent crystals doped with 0.91–5.91 mol% MgO were compared and comprised two Concentration Thresholds at ~3.0 and ~5.5 mol% MgO. The main band parameters of OH stretching vibrations in IR absorption spectra (frequency, half-width, intensity) displayed abrupt changes near the Concentration Threshold at 5.5 mol% MgO. The OH stretching-vibration band shifted to higher frequency by ~50 cm^–1 because of the formation of (Mg_Li)^+–(Mg_Nb)^3––OH^–complexes upon reaching the second Mg Concentration Threshold.
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Concentration Threshold effect on properties of zinc doped lithium niobate crystals
Journal of the American Ceramic Society, 2017Co-Authors: M N Palatnikov, N V Sidorov, O. V. Makarova, D. V. Manukovskaya, Ludmila A. Aleshina, A. V. KadetovaAbstract:Results of LiNbO3:Zn researches often diverge because sharp changes in physicochemical characteristics of the system melt-crystal that occur at doping are usually not taken into consideration. When a series of doped crystals is grown Zn is usually added to the melt with step 1.5-2 mol%. This obstructs detection of exact Threshold Concentration. We have grown LiNbO3:Zn crystals doped by 4.0÷9.0 mol% ZnO with step ~1 mol%. Around the dopant, Threshold Concentration step was narrowed to ~0.1 mol%. We have researched physicochemical properties of the system melt-crystal and structure evolution by Raman spectroscopy and full-profile analysis of XRD. We have detected exact Threshold Concentration for LiNbO3:Zn and concluded that crystals doped by preThreshold Concentrations of ZnO are the best for most applications because of the higher optical homogeneity.
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Manifestation of structural features of LiNbO 3 :Zn and LiNbO 3 :Mg crystals in their IR absorption spectra in the stretching region of OH – groups
Inorganic Materials, 2017Co-Authors: N V Sidorov, L. A. Bobreva, M N Palatnikov, N. N. NovikovaAbstract:Analysis of IR absorption spectra of LiNbO3:Zn (0.04–4.46 mol % ZnO) and LiNbO3:Mg (0.19–5.91 mol % MgO) single crystals in the stretching region of OH– groups has been used to gain insight into composition-dependent structural changes in the crystals. The results demonstrate that, characteristically, the OH– groups occupy different sites in the doped and congruent LiNbO3 crystals and have different quasielastic O–H bond constants in their structure. In stoichiometric lithium niobate crystals, all of the OH– sites and quasi-elastic O–H bond constants are identical. At Threshold Zn and Mg dopant Concentrations, the frequencies, widths, and intensities of the observed lines change sharply. The linewidths in the spectra of the LiNbO3:Zn crystals near their first Concentration Threshold (≈2.0 mol % ZnO) and the LiNbO3:Mg crystals near their first and second Concentration Thresholds (≈3.0 and 5.5 mol % MgO) decrease markedly, indicating ordering of the position of the OH– groups in the structure of the crystals.
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Concentration Threshold effect on properties of zinc‐doped lithium niobate crystals
Journal of the American Ceramic Society, 2017Co-Authors: M N Palatnikov, N V Sidorov, O. V. Makarova, D. V. Manukovskaya, Ludmila A. Aleshina, A. V. KadetovaAbstract:Results of LiNbO3:Zn researches often diverge because sharp changes in physicochemical characteristics of the system melt-crystal that occur at doping are usually not taken into consideration. When a series of doped crystals is grown Zn is usually added to the melt with step 1.5-2 mol%. This obstructs detection of exact Threshold Concentration. We have grown LiNbO3:Zn crystals doped by 4.0÷9.0 mol% ZnO with step ~1 mol%. Around the dopant, Threshold Concentration step was narrowed to ~0.1 mol%. We have researched physicochemical properties of the system melt-crystal and structure evolution by Raman spectroscopy and full-profile analysis of XRD. We have detected exact Threshold Concentration for LiNbO3:Zn and concluded that crystals doped by preThreshold Concentrations of ZnO are the best for most applications because of the higher optical homogeneity.
A. V. Kadetova - One of the best experts on this subject based on the ideXlab platform.
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Concentration Threshold effect on properties of zinc doped lithium niobate crystals
Journal of the American Ceramic Society, 2017Co-Authors: M N Palatnikov, N V Sidorov, O. V. Makarova, D. V. Manukovskaya, Ludmila A. Aleshina, A. V. KadetovaAbstract:Results of LiNbO3:Zn researches often diverge because sharp changes in physicochemical characteristics of the system melt-crystal that occur at doping are usually not taken into consideration. When a series of doped crystals is grown Zn is usually added to the melt with step 1.5-2 mol%. This obstructs detection of exact Threshold Concentration. We have grown LiNbO3:Zn crystals doped by 4.0÷9.0 mol% ZnO with step ~1 mol%. Around the dopant, Threshold Concentration step was narrowed to ~0.1 mol%. We have researched physicochemical properties of the system melt-crystal and structure evolution by Raman spectroscopy and full-profile analysis of XRD. We have detected exact Threshold Concentration for LiNbO3:Zn and concluded that crystals doped by preThreshold Concentrations of ZnO are the best for most applications because of the higher optical homogeneity.
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Concentration Threshold effect on properties of zinc‐doped lithium niobate crystals
Journal of the American Ceramic Society, 2017Co-Authors: M N Palatnikov, N V Sidorov, O. V. Makarova, D. V. Manukovskaya, Ludmila A. Aleshina, A. V. KadetovaAbstract:Results of LiNbO3:Zn researches often diverge because sharp changes in physicochemical characteristics of the system melt-crystal that occur at doping are usually not taken into consideration. When a series of doped crystals is grown Zn is usually added to the melt with step 1.5-2 mol%. This obstructs detection of exact Threshold Concentration. We have grown LiNbO3:Zn crystals doped by 4.0÷9.0 mol% ZnO with step ~1 mol%. Around the dopant, Threshold Concentration step was narrowed to ~0.1 mol%. We have researched physicochemical properties of the system melt-crystal and structure evolution by Raman spectroscopy and full-profile analysis of XRD. We have detected exact Threshold Concentration for LiNbO3:Zn and concluded that crystals doped by preThreshold Concentrations of ZnO are the best for most applications because of the higher optical homogeneity.
N V Sidorov - One of the best experts on this subject based on the ideXlab platform.
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Optical Anomalies in LiNbO 3 :Mg Crystals
Optics and Spectroscopy, 2019Co-Authors: N V Sidorov, L. A. Bobreva, M N Palatnikov, N. A. Teplyakova, O. V. MakarovaAbstract:We have observed that LiNbO3:Mg (0.19–5.91 mol % MgO) crystals experience rearrangements in their defect structure with increasing Concentration of Mg and exhibit optical anomalies related with them, which have a Threshold character. We have shown that, at Mg Concentrations close to the first Concentration Threshold at ~3.0 mol % MgO, the optical homogeneity of the crystals increases. When the Mg Concentration approaches the second Concentration Threshold, we have revealed a significant shift (by ~50 cm–1 compared to that in other crystals) of the entire IR absorption spectrum in the range of stretching vibrations of OH groups to the high-frequency range, a sharp decrease in the number of protons, and a jumpwise shift of the absorption edge in the short-wavelength range. We have shown that the shift occurs because all NbLi point defects are replaced by Mg cations near the Concentration Threshold at 5.5 mol % MgO, and, subsequently, Mg cations occupy only positions of Li and Nb cations of an ideal stoichiometric structure, forming MgLi and MgNb point defects.
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Complex Defects in Mg-Doped Lithium Niobate Crystals Over a Wide Concentration Range and Their Manifestation in IR Absorption Spectra in the OH Stretching Vibration Region
Journal of Applied Spectroscopy, 2019Co-Authors: N V Sidorov, L. A. Bobreva, M N PalatnikovAbstract:Structural defects of nominally pure congruent and stoichiometric LiNbO_3 crystals and a series of congruent crystals doped with 0.91–5.91 mol% MgO were compared and comprised two Concentration Thresholds at ~3.0 and ~5.5 mol% MgO. The main band parameters of OH stretching vibrations in IR absorption spectra (frequency, half-width, intensity) displayed abrupt changes near the Concentration Threshold at 5.5 mol% MgO. The OH stretching-vibration band shifted to higher frequency by ~50 cm^–1 because of the formation of (Mg_Li)^+–(Mg_Nb)^3––OH^–complexes upon reaching the second Mg Concentration Threshold.
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Concentration Threshold effect on properties of zinc doped lithium niobate crystals
Journal of the American Ceramic Society, 2017Co-Authors: M N Palatnikov, N V Sidorov, O. V. Makarova, D. V. Manukovskaya, Ludmila A. Aleshina, A. V. KadetovaAbstract:Results of LiNbO3:Zn researches often diverge because sharp changes in physicochemical characteristics of the system melt-crystal that occur at doping are usually not taken into consideration. When a series of doped crystals is grown Zn is usually added to the melt with step 1.5-2 mol%. This obstructs detection of exact Threshold Concentration. We have grown LiNbO3:Zn crystals doped by 4.0÷9.0 mol% ZnO with step ~1 mol%. Around the dopant, Threshold Concentration step was narrowed to ~0.1 mol%. We have researched physicochemical properties of the system melt-crystal and structure evolution by Raman spectroscopy and full-profile analysis of XRD. We have detected exact Threshold Concentration for LiNbO3:Zn and concluded that crystals doped by preThreshold Concentrations of ZnO are the best for most applications because of the higher optical homogeneity.
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Manifestation of structural features of LiNbO 3 :Zn and LiNbO 3 :Mg crystals in their IR absorption spectra in the stretching region of OH – groups
Inorganic Materials, 2017Co-Authors: N V Sidorov, L. A. Bobreva, M N Palatnikov, N. N. NovikovaAbstract:Analysis of IR absorption spectra of LiNbO3:Zn (0.04–4.46 mol % ZnO) and LiNbO3:Mg (0.19–5.91 mol % MgO) single crystals in the stretching region of OH– groups has been used to gain insight into composition-dependent structural changes in the crystals. The results demonstrate that, characteristically, the OH– groups occupy different sites in the doped and congruent LiNbO3 crystals and have different quasielastic O–H bond constants in their structure. In stoichiometric lithium niobate crystals, all of the OH– sites and quasi-elastic O–H bond constants are identical. At Threshold Zn and Mg dopant Concentrations, the frequencies, widths, and intensities of the observed lines change sharply. The linewidths in the spectra of the LiNbO3:Zn crystals near their first Concentration Threshold (≈2.0 mol % ZnO) and the LiNbO3:Mg crystals near their first and second Concentration Thresholds (≈3.0 and 5.5 mol % MgO) decrease markedly, indicating ordering of the position of the OH– groups in the structure of the crystals.
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Concentration Threshold effect on properties of zinc‐doped lithium niobate crystals
Journal of the American Ceramic Society, 2017Co-Authors: M N Palatnikov, N V Sidorov, O. V. Makarova, D. V. Manukovskaya, Ludmila A. Aleshina, A. V. KadetovaAbstract:Results of LiNbO3:Zn researches often diverge because sharp changes in physicochemical characteristics of the system melt-crystal that occur at doping are usually not taken into consideration. When a series of doped crystals is grown Zn is usually added to the melt with step 1.5-2 mol%. This obstructs detection of exact Threshold Concentration. We have grown LiNbO3:Zn crystals doped by 4.0÷9.0 mol% ZnO with step ~1 mol%. Around the dopant, Threshold Concentration step was narrowed to ~0.1 mol%. We have researched physicochemical properties of the system melt-crystal and structure evolution by Raman spectroscopy and full-profile analysis of XRD. We have detected exact Threshold Concentration for LiNbO3:Zn and concluded that crystals doped by preThreshold Concentrations of ZnO are the best for most applications because of the higher optical homogeneity.
Eva Furrow - One of the best experts on this subject based on the ideXlab platform.
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determination of a serum total calcium Concentration Threshold for accurate prediction of ionized hypercalcemia in dogs with and without hyperphosphatemia
Journal of Veterinary Internal Medicine, 2020Co-Authors: Elizabeth M. Groth, Dennis J. Chew, Jody P. Lulich, Megan Tommet, Aaron K. Rendahl, Brian D. Husbands, Eva FurrowAbstract:BACKGROUND: Total serum calcium (tCa) Concentrations are poorly predictive of ionized calcium (iCa) status in dogs. HYPOTHESIS: There is an optimal Threshold of tCa Concentration that is highly predictive of ionized hypercalcemia and this Threshold is higher in hyperphosphatemic dogs as compared to nonhyperphosphatemic dogs. ANIMALS: Nonhyperphosphatemic (n = 1593) and hyperphosphatemic (n = 250) adult dogs. METHODS: Retrospective medical record review of paired tCa and iCa Concentration measurements in dogs presented to a university teaching hospital over a 5‐year period. Positive and negative predictive values, sensitivity, and specificity were calculated for tCa Concentration Thresholds of 11.0‐15.0 mg/dL (upper limit of laboratory reference interval = 11.5 mg/dL) in nonhyperphosphatemic and hyperphosphatemic groups. RESULTS: In nonhyperphosphatemic dogs, an optimal tCa Concentration Threshold of 12.0 mg/dL resulted in a positive predictive value of 93% (95% confidence interval [CI], 84%‐98%) and sensitivity of 52% (95% CI, 43%‐61%) for ionized hypercalcemia. An optimal tCa Concentration Threshold was not identified for hyperphosphatemic dogs. The nonhyperphosphatemic dogs had a higher prevalence of ionized hypercalcemia than the hyperphosphatemic dogs (7 versus 3%, P = .04) and a lower prevalence of ionized hypocalcemia (23 versus 62%, respectively; P < .001). CONCLUSIONS AND CLINICAL IMPORTANCE: High tCa Concentrations are strongly predictive of ionized hypercalcemia in nonhyperphosphatemic adult dogs and should prompt further diagnostic testing to determine the underlying cause of hypercalcemia. In this population, dogs without increased tCa Concentrations rarely had ionized hypercalcemia, but iCa Concentrations still should be evaluated in patients with tCa Concentrations within the reference interval if there is clinical suspicion for calcium abnormalities.
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Determination of a serum total calcium Concentration Threshold for accurate prediction of ionized hypercalcemia in dogs with and without hyperphosphatemia.
Journal of veterinary internal medicine, 2019Co-Authors: Elizabeth M. Groth, Dennis J. Chew, Jody P. Lulich, Megan Tommet, Aaron K. Rendahl, Brian D. Husbands, Eva FurrowAbstract:BACKGROUND: Total serum calcium (tCa) Concentrations are poorly predictive of ionized calcium (iCa) status in dogs. HYPOTHESIS: There is an optimal Threshold of tCa Concentration that is highly predictive of ionized hypercalcemia and this Threshold is higher in hyperphosphatemic dogs as compared to nonhyperphosphatemic dogs. ANIMALS: Nonhyperphosphatemic (n = 1593) and hyperphosphatemic (n = 250) adult dogs. METHODS: Retrospective medical record review of paired tCa and iCa Concentration measurements in dogs presented to a university teaching hospital over a 5‐year period. Positive and negative predictive values, sensitivity, and specificity were calculated for tCa Concentration Thresholds of 11.0‐15.0 mg/dL (upper limit of laboratory reference interval = 11.5 mg/dL) in nonhyperphosphatemic and hyperphosphatemic groups. RESULTS: In nonhyperphosphatemic dogs, an optimal tCa Concentration Threshold of 12.0 mg/dL resulted in a positive predictive value of 93% (95% confidence interval [CI], 84%‐98%) and sensitivity of 52% (95% CI, 43%‐61%) for ionized hypercalcemia. An optimal tCa Concentration Threshold was not identified for hyperphosphatemic dogs. The nonhyperphosphatemic dogs had a higher prevalence of ionized hypercalcemia than the hyperphosphatemic dogs (7 versus 3%, P = .04) and a lower prevalence of ionized hypocalcemia (23 versus 62%, respectively; P
O. V. Makarova - One of the best experts on this subject based on the ideXlab platform.
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Optical Anomalies in LiNbO 3 :Mg Crystals
Optics and Spectroscopy, 2019Co-Authors: N V Sidorov, L. A. Bobreva, M N Palatnikov, N. A. Teplyakova, O. V. MakarovaAbstract:We have observed that LiNbO3:Mg (0.19–5.91 mol % MgO) crystals experience rearrangements in their defect structure with increasing Concentration of Mg and exhibit optical anomalies related with them, which have a Threshold character. We have shown that, at Mg Concentrations close to the first Concentration Threshold at ~3.0 mol % MgO, the optical homogeneity of the crystals increases. When the Mg Concentration approaches the second Concentration Threshold, we have revealed a significant shift (by ~50 cm–1 compared to that in other crystals) of the entire IR absorption spectrum in the range of stretching vibrations of OH groups to the high-frequency range, a sharp decrease in the number of protons, and a jumpwise shift of the absorption edge in the short-wavelength range. We have shown that the shift occurs because all NbLi point defects are replaced by Mg cations near the Concentration Threshold at 5.5 mol % MgO, and, subsequently, Mg cations occupy only positions of Li and Nb cations of an ideal stoichiometric structure, forming MgLi and MgNb point defects.
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Concentration Threshold effect on properties of zinc doped lithium niobate crystals
Journal of the American Ceramic Society, 2017Co-Authors: M N Palatnikov, N V Sidorov, O. V. Makarova, D. V. Manukovskaya, Ludmila A. Aleshina, A. V. KadetovaAbstract:Results of LiNbO3:Zn researches often diverge because sharp changes in physicochemical characteristics of the system melt-crystal that occur at doping are usually not taken into consideration. When a series of doped crystals is grown Zn is usually added to the melt with step 1.5-2 mol%. This obstructs detection of exact Threshold Concentration. We have grown LiNbO3:Zn crystals doped by 4.0÷9.0 mol% ZnO with step ~1 mol%. Around the dopant, Threshold Concentration step was narrowed to ~0.1 mol%. We have researched physicochemical properties of the system melt-crystal and structure evolution by Raman spectroscopy and full-profile analysis of XRD. We have detected exact Threshold Concentration for LiNbO3:Zn and concluded that crystals doped by preThreshold Concentrations of ZnO are the best for most applications because of the higher optical homogeneity.
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Concentration Threshold effect on properties of zinc‐doped lithium niobate crystals
Journal of the American Ceramic Society, 2017Co-Authors: M N Palatnikov, N V Sidorov, O. V. Makarova, D. V. Manukovskaya, Ludmila A. Aleshina, A. V. KadetovaAbstract:Results of LiNbO3:Zn researches often diverge because sharp changes in physicochemical characteristics of the system melt-crystal that occur at doping are usually not taken into consideration. When a series of doped crystals is grown Zn is usually added to the melt with step 1.5-2 mol%. This obstructs detection of exact Threshold Concentration. We have grown LiNbO3:Zn crystals doped by 4.0÷9.0 mol% ZnO with step ~1 mol%. Around the dopant, Threshold Concentration step was narrowed to ~0.1 mol%. We have researched physicochemical properties of the system melt-crystal and structure evolution by Raman spectroscopy and full-profile analysis of XRD. We have detected exact Threshold Concentration for LiNbO3:Zn and concluded that crystals doped by preThreshold Concentrations of ZnO are the best for most applications because of the higher optical homogeneity.
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Specific features of growth and structure of LiNbO3 : Zn crystals near the ZnO Concentration Threshold of 6.76 mol %
Technical Physics, 2017Co-Authors: N V Sidorov, M N Palatnikov, A. A. Yanichev, R. A. Titov, O. V. MakarovaAbstract:The crystallization conditions and Raman spectra of LiNbO3 : Zn crystals (0.02–8.91 mol % ZnO in the melt) have been investigated. It has been established that the most favorable conditions for growing optically and compositionally homogeneous heavily doped LiNbO3 : Zn crystals, which are characterized by a low photorefractive effect, are implemented in the ZnO Concentration range of ~4.0–6.76 mol % in the melt. Since the distribution coefficient K eff decreases significantly with an increase in the ZnO Concentration in the melt, one can obtain LiNbO3 : Zn crystals with significantly different defect structures but identical zinc Concentrations. A change in the zinc Concentration in crystals has been shown to induce a stepwise change in the sequence order of the main (Li and Nb) and doping (Zn) cations and vacancies and stepwise anisotropic expansion of the oxygen octahedra along the polar axis. The number of kinks in the Concentration behavior of the spectral-line widths (five kinks for the lines with frequencies of 630 (A 1(TO)) and 876 cm–1 (A 1(LO))) significantly exceeds the number of Thresholds (two) known from the literature.
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specific features of growth and structure of linbo3 zn crystals near the zno Concentration Threshold of 6 76 mol
Technical Physics, 2017Co-Authors: N V Sidorov, M N Palatnikov, A. A. Yanichev, R. A. Titov, O. V. MakarovaAbstract:The crystallization conditions and Raman spectra of LiNbO3 : Zn crystals (0.02–8.91 mol % ZnO in the melt) have been investigated. It has been established that the most favorable conditions for growing optically and compositionally homogeneous heavily doped LiNbO3 : Zn crystals, which are characterized by a low photorefractive effect, are implemented in the ZnO Concentration range of ~4.0–6.76 mol % in the melt. Since the distribution coefficient K eff decreases significantly with an increase in the ZnO Concentration in the melt, one can obtain LiNbO3 : Zn crystals with significantly different defect structures but identical zinc Concentrations. A change in the zinc Concentration in crystals has been shown to induce a stepwise change in the sequence order of the main (Li and Nb) and doping (Zn) cations and vacancies and stepwise anisotropic expansion of the oxygen octahedra along the polar axis. The number of kinks in the Concentration behavior of the spectral-line widths (five kinks for the lines with frequencies of 630 (A 1(TO)) and 876 cm–1 (A 1(LO))) significantly exceeds the number of Thresholds (two) known from the literature.