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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krylov A. S., Gerasimova Y. V., Vtyurin A. N., Fokina V. D., Laptash N. M., Voit E. I.
Заглавие : Raman scattering study of the phase transition in the (NH4)(3)WO3F3 oxyfluoride
Разночтения заглавия :авие SCOPUS: A Raman scattering study of the phase transition in the (NH 4)3WO3F3 oxyfluoride
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2006. - Vol. 48, Is. 7. - P1356-1362. - ISSN 1063-7834, DOI 10.1134/S1063783406070237
Примечания : Cited References: 11
Аннотация: The Raman scattering spectra of polycrystalline samples of the (NH4)(3)WO3F3 perovskite-like oxyfluoride were measured at frequencies of 70-3600 cm(-1) in the temperature range 93-323 K, including the transition from the orientationally disordered cubic phase to the low-symmetry phase. Transitional anomalies in the spectral parameters were revealed in the frequency ranges of internal vibrations of the ammonium ions and WO3F3 octahedral groups. An analysis of the experimental results allowed the conclusion that the phase transition under study is associated primarily with the ordering of the octahedral groups.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mel'nikova S. V., Laptash N. M., Zhogal' A. L.
Заглавие : Phase transitions in the oxyfluoride (NH4)(3)NbOF6
Разночтения заглавия :авие SCOPUS: Phase transitions in the oxyfluoride (NH4)3NbOF 6
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2007. - Vol. 49, Is. 5. - P958-962. - ISSN 1063-7834, DOI 10.1134/S1063783407050253
Примечания : Cited References: 11
Предметные рубрики: RAY-DIFFRACTION INVESTIGATIONS
DISTORTED PHASES
SYMMETRY
DISORDER
CRYSTAL
Аннотация: (NH4)(3)NbOF6 single crystals were grown, polarization-optical studies were performed, and birefringence was measured over the temperature range 90-500 K. A sequence of first-order structural phase transitions was found at temperatures T (1 down arrow) = 259.7 K and T (2 down arrow) = 257.7 K with temperature hysteresis delta T-1 = 0.9 K and delta T-2 = 1.9 K. The transitions are accompanied by twinning and the following change in the crystal symmetry: cubic paired left right arrows tetragonal paired left right arrows monoclinic. Optical second harmonic generation is found to occur at room temperature, which indicates that the cubic phase is not centrosymmetric. It is assumed that the phase transitions are ferroelastic and ferroelectric in nature.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Fokina V. D., Gorev M. V., Bogdanov E. V., Molokeev M. S., Bovina A. F., Kocharova A. G.
Заглавие : Effect of deuteration on the thermal properties and structural parameters of the (NH4)(2)WO2F4 oxyfluoride
Разночтения заглавия :авие SCOPUS: Effect of deuteration on the thermal properties and structural parameters of the (NH4)2WO2F4 oxyfluoride
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2007. - Vol. 49, Is. 6. - P1149-1156. - ISSN 1063-7834, DOI 10.1134/S1063783407060212
Примечания : Cited References: 11
Предметные рубрики: PEROVSKITE-LIKE OXYFLUORIDES
PHASE-TRANSITIONS
(NH4)(3)WO3F3
(NH4)(3)TIOF5
Аннотация: The thermal properties and structure of (ND4)(2)WO2F4 crystals are investigated. It is established that deuteration does not lead to a change in the symmetry of the initial phase Cmcm but considerably decreases the extent of its disordering, which, in turn, brings about a substantial decrease in the phase transition entropy. Apart from the anomalies associated with phase transitions characteristic of the protonic compound, the heat capacity exhibits two additional anomalies. Analysis of the phase diagram of the deuterated crystal reveals a triple point at a pressure p = 0.18 GPa, which is predicted for (NH4)(2)WO2F4 at about 0.7 GPa.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krylov A. S., Vtyurin A. N., Fokina V. D., Goryainov S. V., Kocharova A. G.
Заглавие : Raman spectroscopic study of the phase transitions in the Cs2NH4WO3F3 oxyfluoride
Разночтения заглавия :авие SCOPUS: Raman spectroscopic study of the phase transitions in the Cs 2NH4WO3F3 oxyfluoride
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2006. - Vol. 48: 17th All-Russia Conference on the Physics of Ferroelectrics (VKS-XVII) (JUN 26-JUL 01, 2005, Penza, RUSSIA), Is. 6. - P1064-1066. - ISSN 1063-7834, DOI 10.1134/S106378340606014X
Примечания : Cited References: 5
Аннотация: The Raman spectra of Cs2NH4WO3F3 elpasolite crystals are studied in the temperature range 93373 K at pressures of up to 6.3 GPa. No indication of a phase transition is revealed from the Raman spectra as the temperature decreases to 93 K. An analysis of the Raman spectra measured under pressure demonstrates that the Cs2NH4WO3F3 elpasolite crystals undergo a phase transition at a pressure of 2.58 GPa. Judging from the behavior of the pressure dependences of the vibrational frequencies, the revealed phase transition is associated with the lowering of the symmetry of the WO3F3 octahedra.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mel'nikova S. V., Fokina V. D., Laptash N. M.
Заглавие : Phase transitions in oxyfluoride (NH4)(2)WO2F4
Разночтения заглавия :авие SCOPUS: Phase transitions in oxyfluoride (NH4)2WO 2F4
Место публикации : Phys. Solid State: SPRINGER, 2006. - Vol. 48, Is. 1. - P117-121. - ISSN 1063-7834, DOI 10.1134/S1063783406010239
Примечания : Cited References: 11
Аннотация: (NH4)(2)WO2F4 single crystals are grown, and their polarization-optical, calorimetric, and birefringence properties are studied in the temperature range 90-350K. A first-order structural phase transition is found to occur at T-01 up arrow = 202K with thermal hysteresis of Delta T-01 approximate to 6-12K. The phase transition is accompanied by twinning and modification of the symmetry Cmcm↔ (1) over bar. An additional weak anomaly in the differential scanning calorimeter signal is found at T-02 approximate to 170K. The total thermal effect of both anomalies is = 3200 +/- 400 J/mol and Sigma Delta S-i = 16.5 +/- 2.0 J/mol K. The phase transition at T-01 is of the order-disorder type.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krylov A. S., Gerasimova J. V., Vtyurin A. N., Fokina V. D., Laptash N. M., Voyt E. I.
Заглавие : A study of phase transition in (NH4)(3)WO3F3 oxyfluoride by Raman scattering
Разночтения заглавия :авие SCOPUS: A study of phase transition in (NH4)3WO 3F3 oxyfluoride by Raman scattering
Место публикации : Phys. Status Solidi B. - 2006. - Vol. 243, Is. 2. - P.435-441. - ISSN 0370-1972, DOI 10.1002/pssb.200541259
Примечания : Cited References: 11
Предметные рубрики: ELPASOLITE RB2KSCF6
Аннотация: Raman scattering spectra of perovskite-like (NH4)(3)WO3F3 oxyfluoride are studied in the 70-3600 cm(-1) frequency range and the 93-323 K temperature range including the transition point from orientationally disordered cubic phase into the lower symmetry one. Internal vibrations of ammonium ions and WO3F3 octahedra have been found to exhibit transition anomalies. Analysis of measurements suggests that the transition under study is due mainly to the ordering of octahedra.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Vtyurin A. N., Krylov A. S., Gerasimova Y. V., Fokina V. D., Laptash N. M., Voit E. I.
Заглавие : Raman spectroscopic study of the phase transitions in the (NH4)(3)WO3F3 oxyfluoride
Разночтения заглавия :авие SCOPUS: Raman spectroscopic study of the phase transitions in the (NH 4)3WO3F3 oxyfluoride
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2006. - Vol. 48: 17th All-Russia Conference on the Physics of Ferroelectrics (VKS-XVII) (JUN 26-JUL 01, 2005, Penza, RUSSIA), Is. 6. - P1067-1069. - ISSN 1063-7834, DOI 10.1134/S1063783406060151
Примечания : Cited References: 7
Аннотация: The Raman spectra of (NH4)(3)WO3F3 perovskite-like oxyfluorides are measured in the frequency range 70-3600 cm(-1). The anomalies observed in the spectral parameters upon phase transitions at a temperature of 200 K under atmospheric pressure and at room temperature under a pressure of 1.4 GPa are interpreted.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Fokina V. D., Bovina A. F., Bogdanov E. V., Molokeev M. S., Kocharova A. G., Pogorel'tsev E. I., Laptash N. M.
Заглавие : Mechanism and nature of phase transitions in the (NH4)(3)MoO3F3 oxyfluoride
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2008. - Vol. 50, Is. 3. - P515-524. - ISSN 1063-7834, DOI 10.1134/S1063783408030219
Примечания : Cited References: 13
Предметные рубрики: (NH4)(2)WO2F4
DIFFRACTION
CS
Аннотация: The temperature dependences of the heat capacity, the unit cell parameter, and the permittivity for the (NH4)(3)MoO3F3 cryolite (space group Fm (3) over barm) are investigated. It is revealed that the compound undergoes ferroelectric and ferroelastic structural phase transitions at temperatures of 297 and 205 K, respectively. The mechanism of structural distortions is discussed in terms of the entropy parameters, pressure-temperature phase diagrams, and electron density maps for critical atoms. An analysis is made of the influence of the cation size and shape on the phase transitions in oxyfluorides of the general formula A(2)A'MO3F3 (A,A' = NH4, K; M = Mo, W).
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fokina V. D., Bogdanov E. V., Gorev M. V., Molokeev M. S., Pogorel'tsev E. I., Flerov I. N., Laptash N. M.
Заглавие : Phase transitions in the (NH4)(2)NbOF5 oxyfluoride
Коллективы :
Разночтения заглавия :авие SCOPUS: Phase transitions in the (NH4)2NbOF5 oxyfluoride
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2010. - Vol. 52, Is. 4. - P781-788. - ISSN 1063-7834, DOI 10.1134/S1063783410040189
Примечания : Cited References: 13. - We would like to thank A. A. Udovenko (Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, Russia) for kindly supplied detailed data on the atomic coordinates in the structure of the (NHINF4/INF)INF2/INFNbOFINF5/INF oxyfluoride.This study was supported by the Russian Foundation for Basic Research (project no. 09-02-00062) and the Council on Grants from the President of the Russian Federation for Support of Leading Scientific Schools of the Russian Federation (grant no. NSh-1011.2008.2).
Предметные рубрики: CRYSTAL-STRUCTURE
(NH4)(2)WO2F4
MECHANISM
DISORDER
Аннотация: The thermal and dielectric properties of the (NH4)(2)NbOF5 oxyfluoride have been investigated. It has been established that the structural phase transitions Cmc2(1) - C2 - Ia observed at the temperatures T (1) = 258.0 K and T (2) = 218.9 K exhibit a nonferroelectric nature. The hydrostatic pressure, which stabilizes the initial phase and destabilizes the low-temperature phase, hardly affects the temperature range of stability of the intermediate phase. The model of sequential ordering of the structural elements due to phase transitions has been analyzed using experimental data on the entropies of the phase transitions.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorev M., Bogdanov E. V., Flerov I. N., Laptash N. M.
Заглавие : Thermal expansion, phase diagrams and barocaloric effects in (NH4)(2)NbOF5
Коллективы :
Разночтения заглавия :авие SCOPUS: Thermal expansion, phase diagrams and barocaloric effects in (NH 4)2NbOF5
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2010. - Vol. 22, Is. 18. - Ст.185901. - ISSN 0953-8984, DOI 10.1088/0953-8984/22/18/185901
Примечания : Cited References: 17. - This work was supported in part by the Krasnoyarsk Regional Foundation for Support of Scientific and Scientific-Technological Investigations and RFBR in the framework of project 'Siberia' (Grant No. 09-02-98001), and the Council on Grants from the President of the Russian Federation for Support of Leading Scientific Schools (project No. Nsh-1011.2008.2).
Предметные рубрики: CRYSTAL-STRUCTURE
SOLID-STATE
OXYFLUORIDE
TRANSITION
ANION
Ключевые слова (''Своб.индексиров.''): antiferromagnets--ferromagnets--heat capacities--high stress--intermediate phase--pippard relations--structural phase transition--transition temperature--uniaxial pressures--financial data processing--phase diagrams--phase transitions--thermal stress--tools--thermal expansion
Аннотация: The thermal expansion along the a, b and c axes of a (NH4)(2)NbOF5 crystal was measured from 120 to 300 K. Anomalies of alpha(T) associated with previously reported phase transitions Cmc2(1) - C-2 - I a were observed along all directions at T-1 = 259.3 K and T-2 = 220.5 K. The analysis of thermal expansion and heat capacity in the frame of the Pippard relations has permitted us to determine the uniaxial pressure derivatives of the transition temperatures dT/d sigma(i). The T-sigma(i) phase diagrams have shown a tendency for the intermediate phase to disappear at high stress along the b and c axes. Intensive and extensive barocaloric effects near the structural phase transitions were found to be comparable with the caloric parameters of some ferroelectrics, ferromagnets and antiferromagnets.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bogdanov E. V., Vasil'ev A. D., Flerov I. N., Laptash N. M.
Заглавие : Effect of cation substitution in fluorine-oxygen molybdates (NH4)(2-x) A (x) MoO2F4
Разночтения заглавия :авие SCOPUS: Effect of cation substitution in fluorine-oxygen molybdates (NH4)2 - xAxMoO2F4
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 53, Is. 2. - P303-308. - ISSN 1063-7834, DOI 10.1134/S1063783411020065
Примечания : Cited References: 11. - This study was supported by the Russian Foundation for Basic Research (project no. 09-02-00062) and the Council on Grants from the President of the Russian Federation for Support of Leading Scientific Schools of the Russian Federation (project no. NSh-1011.2008.2).
Предметные рубрики: PHASE-TRANSITIONS
CRYSTALS
(NH4)(2)WO2F4
DIFFRACTION
OXYFLUORIDE
MECHANISM
DISORDER
Аннотация: Thermophysical and structural studies of (NH4)(2 - x) A (x) MoO2F4 (A = Cs, Rb, K) solid solutions of oxyfluorides have been performed. The character of the influence of cation substitutions on the stability of the initial phase (space group Cmcm) and on the mechanism of phase transitions has been elucidated.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorev M. V., Flerov I. N., Bogdanov E. V., Voronov V. N., Laptash N. M.
Заглавие : Barocaloric effect near the structural phase transition in the Rb2KTiOF5 oxyfluoride
Коллективы :
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2010. - Vol. 52, Is. 2. - P377-383. - ISSN 1063-7834, DOI 10.1134/S1063783410020253
Примечания : Cited References: 21. - This study was supported by the Siberian Branch of the Russian Academy of Sciences (Interdisciplinary Integration Project no. 34), the Russian Foundation for Basic Research and the Krasnoyarsk Regional Scientific Foundation within the framework of the "Sibir'" Project (project no. 09-02-98001), and the Council on Grants from the President of the Russian Federation for Support of the Leading Scientific Schools of the Russian Federation (grant no. NSh-1011.2008.2).
Предметные рубрики: HEAT-CAPACITY
PRESSURE
Аннотация: The barocaloric effect (BCE) in the oxyfluoride Rb2KTiOF5 has been studied in the vicinity of the structural phase transition at a temperature of 215 K in the pressure range 0-0.6 GPa. It has been established that the extensive and intensive barocaloric effects are Delta S-BCE similar to -46 J/kg K and Delta T (AD) similar to 18 K, respectively, over a wide temperature range 215-280 K. The studies performed have shown that the external hydrostatic pressure is a very effective tool for changing the entropy and temperature of the crystals which undergo structural phase transitions accompanied by a large change in the entropy.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mel'nikova S. V., Laptash N. M.
Заглавие : Phase transitions in orthorhombic oxyfluoride (NH4)(2)MoO2F4
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2008. - Vol. 50, Is. 3. - P511-514. - ISSN 1063-7834, DOI 10.1134/S1063783408030207
Примечания : Cited References: 15
Предметные рубрики: (NH4)(2)WO2F4
Аннотация: (NH4)(2)MoO2F4 single crystals were grown and studied using polarization-optical methods, and the birefringence was measured in the temperature range 90-350 K. The following sequence of phase transitions is revealed: G(0) reversible arrow G(1) reversible arrow G(2). It is established that the phase transition at delta T-01 approximate to 267 K is of the first order and exhibits thermal hysteresis delta T-01 approximate to 0.6 K. A weak anomaly is found in Delta n(T) at T-02 approximate to 180 K. The crystals are shown to retain the orthorhombic symmetry during the phase transitions.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gerasimova Y. V., Krylov A. S., Vtyurin A. N., Laptash N. M., Goryainov S. V.
Заглавие : A Raman scattering study of the phase transition in the ammonium oxyfluoride (NH4)(3)TiOF5
Разночтения заглавия :авие SCOPUS: A raman scattering study of the phase transition in the ammonium oxyfluoride (NH4)3TiOF5
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2008. - Vol. 50, Is. 8. - P1534-1537. - ISSN 1063-7834, DOI 10.1134/S1063783408080246
Примечания : Cited References: 8
Предметные рубрики: (NH4)(3)WO3F3 OXYFLUORIDE
Аннотация: Raman spectra of a polycrystalline sample of the perovskite-like oxyfluoride (NH4)(3)TiOF5 are measured in the frequency region 100-3600 cm(-1) at temperatures ranging from 91 to 370 K under hydrostatic pressures of up to 9 GPa, which include the range of the phase transition from the orientationally disordered cubic phase to the low-symmetry phase. Anomalies in the spectral parameters due to the phase transition are revealed in the range of vibrations of TiOF5 octahedral groups.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fokina V. D., Bogdanov E. V., Pogorel'tsev E. I., Bondarev V. S., Flerov I. N., Laptash N. M.
Заглавие : Calorimetric and dielectric studies of the (NH4)(2)MoO2F4 oxyfluoride
Коллективы :
Разночтения заглавия :авие SCOPUS: Calorimetric and dielectric studies of the (NH4)2MoO2F4 oxyfluoride
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2010. - Vol. 52, Is. 1. - P158-166. - ISSN 1063-7834, DOI 10.1134/S1063783410010282
Примечания : Cited References: 22. - This study was supported by the Russian Foundation for Basic Research ( project no. 09-02-00062).
Предметные рубрики: PHASE-TRANSITIONS
(NH4)(2)WO2F4
DIFFRACTION
MECHANISM
CRYSTALS
Аннотация: The temperature dependences of the heat capacity, dielectric properties, and response to an external pressure and an electric field for the (NH4)(2)MoO2F4 oxyfluoride (space group Cmcm, Z = 4) have been studied. A comparative analysis of the data on the entropy of phase transitions, p-T phase diagrams, permittivity, and anomalous heat capacity in combination with the results of previous studies of the related compounds (NH4)(2)WO2F4 and (ND4)(2)WO2F4 has made it possible to establish that both [MO2F4](2-) anions and ammonium groups play a substantial role in the mechanism and nature of the structural transformations.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Vasiliev A. D., Melnikova S.V., Isaenko L. I.
Заглавие : Orthorhombic aluminium oxyfluoride, AlOF
Место публикации : Acta Crystallogr. Sect. C-Cryst. Struct. Commun. - MALDEN: WILEY-BLACKWELL PUBLISHING, INC, 2009. - Vol. 65. - С. I20-I22. - APR. - ISSN 0108-2701, DOI 10.1107/S0108270109010671
Примечания : Cited Reference Count: 11. - Гранты: This work was supported by the RFFI (grant No. 07-0200442) and the Interdisciplinary Integration Project of the Siberian Branch of the Russian Academy of Sciences (No. 34).Финансирующая организация: RFFI [07-0200442]; Interdisciplinary Integration Project of the Siberian Branch of the Russian Academy of Sciences [34]
Аннотация: Crystals of the title compound were extracted from the bulk of grown SrAlF(5) crystals as unexpected inclusions that were identified as the long sought after aluminium oxyfluoride. The structure of AlOF is built up from tetrahedral and octahedral polyhedra. Each tetrahedron is bisected by a mirror plane, with the Al atom and two vertex anions in the plane. All tetrahedral vertices are positions of competing oxide and fluoride ions and are shared with octahedra. These shared vertices belong to two octahedral edges which join the octahedra to form infinite zigzag chains. The chains are strung along twofold screw axes that run parallel to the unit-cell b axis. The remaining two octahedral vertices are occupied only by fluoride ions. A small deficiency in the occupation of the octahedral Al position was suggested by the refinement. However, the stoichiometry of the compound is AlOF within experimental uncertainty. The Al-F(O) distances are separated into three groups with average values of 1.652 (3) (tetrahedra), 1.800(2) (octahedra) and 1.894 (2) angstrom (octahedra). This structure differs widely from the reported tetragonal phase Al(1-x)O(1-3x)F(1+ 3x) (x = 0.0886) [Kutoglu (1992). Z. Kristallogr. 199, 197-201], which consists solely of octahedral structural units.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Vtyurin A.N., Gerasimova J.V., Krylov A.S., Ivanenko A.A., Shestakov N.P., Laptash N.M., Voyt E.I.
Заглавие : Vibrational spectroscopy of alkaline tungsten oxyfluoride crystals: structure, lattice dynamics, ordering processes, and phase transitions
Место публикации : J. Raman Spectrosc. - MALDEN: WILEY-BLACKWELL, 2010. - Vol. 41, Is. 12. - С. 1784-1791. - DEC. - ISSN 0377-0486, DOI 10.1002/jrs.2637
Примечания : Cited Reference Count: 13. - Гранты: We would like to thank Prof. Igor Flerov for fruitful discussion. Technical assistance of Victor Ouskin is highly appreciated. This work has been supported by the Russian Foundation for Basic Researches, grant no. 08-02-00066-a.Финансирующая организация: Russian Foundation for Basic Researches [08-02-00066-a]
Предметные рубрики:
Ключевые слова (''Своб.индексиров.''): raman scattering--infrared absorption--alcaline tungsten oxyfluorides--phase transitions--alcaline tungsten oxyfluorides--infrared absorption--phasetransitions--raman scattering
Аннотация: Raman scattering (RS) and infrared absorption (IR) of ammonium oxyfluoride crystals (NH(4))(3)WO(3)F(3), (NH(4))(2)KWO(3)F(3), and Cs(2)(NH(4))WO(3)F(3) are compared. Conformation of the WO(3)F(3) octahedral groups has been established; anomalies have been found close to the transition temperatures in the internal vibrational regions of ammonium and WO(3)F(3) groups. The phase transition in (NH(4))(3)WO(3)F(3) is associated mostly with the ordering of octahedral groups and formation of W-O center dot center dot center dot H-N hydrogen bonds. In (NH(4))(2)KWO(3)F(3) crystal, the transition is not related to the ordering processes; CS(2)(NH(4))WO(3)F(3) retains its disordered structure down to 10 K. Copyright (C) 2010 John Wiley & Sons, Ltd.
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18.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Sofronova S.N.
Заглавие : The nonemperical calculations of the lattice dynamics of the oxyfluoride RB2KTiOF5
Коллективы : European Meeting on Ferroelectricity
Место публикации : 12th European Meeting on Ferroelectricity: Abstracts. - 2011. - Ст.PI-21
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Laptash N. M., Udovenko A. A., Vasiliev A. D., Merkulov E. B.
Заглавие : Strong hydrogen bond in the crystal structure design of CuNbOF5·4H2O
Место публикации : J. Solid State Chem. - 2023. - Vol. 318. - Ст.123781. - ISSN 00224596 (ISSN), DOI 10.1016/j.jssc.2022.123781. - ISSN 1095726X (eISSN)
Примечания : Cited References: 40. - We thank Dr. T.B. Emelina for the DFT calculations of uncoordinated [NbOF5]2– anion. The work was partially supported within the frames of the State Order of the Institute of Chemistry, Far Eastern Branch of the Russian Academy of Sciences (project No. FWFN 0205–2022–0003)
Аннотация: Fluoride metal-organic frameworks (MOFs) based on pillared [NbOF5]2– anion have been recently received research attention as ultramicroporous materials for gas storage and separation. The trans-directing property of the NbOF5 octahedron plays a significant role in designing mixed metal oxyfluoride compounds composed of the alternating transition metal polyhedra, which are linked via oxide and fluoride ligands. Mixed metal CuNbOF5·4H2O is the only unique example when the trans-directing properties of [NbOF5]2– are realized in the formation of a strong O–H⋯F hydrogen bond (HB). Well-shaped single crystals of this compound were grown and their structure was refined by X-ray diffraction. Under quasi-isobaric conditions, a phase transition at 88 °C takes place, which is associated with the weakening of HBs and formation of ordinary chains through conventional trans-(O,F) bridges. The character of hydrogen bonding in CuNbOF5·4H2O affects its thermal behavior described by the dehydration and pyrohydrolysis processes.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ming, Hong, Zhao, Yifei, Zhou, Yayun, Molokeev M. S., Wang, Yuanjing, Song, Enhai, Zhang, Qinyuan
Заглавие : Chemical group substitution enables highly efficient Mn4+ luminescence in heterovalent systems
Место публикации : Adv. Optical Mater. - 2023. - Vol. 11, Is. 10. - Ст.2300076. - ISSN 21951071 (eISSN), DOI 10.1002/adom.202300076
Примечания : Cited References: 36. - This work was financially supported by the National Key Research and Development Program of China (2022YFB3503800), the National Science Foundation of China (Grant Nos. 52202170 and 51972117). This work was also funded by RFBR according to the research project No. 19-52-80003
Аннотация: Defects are a double-edged sword for heterovalent metal-ion doping phosphors. Along with the luminescence tunability of phosphors bestowed by defects, their expected luminescence efficiency would also be inevitably lowered due to the presence of these quenching sites. Herein, a chemical group substitution strategy is proposed, where inorganic polyhedrons act as the smallest chemical units during the structural evolution of the doping process. Such a method can not only effectively prevent the defect generation for charge compensation in heterovalent doping systems, but also facilitate the incorporation of activators into the matrix, leading to extremely high luminescence efficiency. The concept is first confirmed energetically favorable by first-principles simulations. As a robust experimental proof, two newly reported Mn4+-incorporated hexavalent organic-inorganic hybrid oxyfluorides (TMA)2BO2F4:Mn4+ (where TMA stands for tetramethylammonium, and B = W6+ or Mo6+) present high quantum efficiency (up to 94.4%) and short lifetime (down to 2.26 ms) that are superior to the commercial red phosphor K2SiF6:Mn4+ (≈84.8%, ≈8.06 ms). Utilizing the differences in decay lifetimes and thermal quenching behaviors of (TMA)2BO2F4:Mn4+ and K2SiF6:Mn4+, a time- and temperature-resolved single-color multiplexing mode with high-safety and easy-access is developed for information security. This work offers an effective strategy to manipulate defect generation in luminescent materials.
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