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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) : 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) : 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) : Molokeev M. S., Vasiliev A. D., Kocharova A. G.
Заглавие : Crystal structures of room- and low-temperature phases in oxyfluoride (NH4)(2)KWO3F3
Место публикации : Powder Diffr. - 2007. - Vol. 22, Is. 3. - P.227-230. - ISSN 0885-7156, DOI 10.1154/1.2759491
Примечания : Cited References: 8. - Cover image: Artwork representing main idea of this article
Ключевые слова (''Своб.индексиров.''): structure determination--rietveld analysis--powder diffraction--phase transition--oxyfluoride
Аннотация: Crystal structures of (NH4)2KWO(3)F(3) at 298 K and 113 K were solved from X-ray powder diffraction data and refined by the Rietveld technique. The compound is isostructural with elpasolite K2NaAlF6 at room temperature with space group Fm-3m, a=8.95850(5) angstrom, V=718.961(7) angstrom(3), Z =4, D-x=3.363 g/cm(3), and M-W=364.02. The structure was refined over 18 parameters to R-wp =12.6%, R-p=10.9%, R-exp=5.03%, and R-B=3.27% from 40 independent reflections. (NH4)2KWO(3)F(3) was transformed upon cooling to a ferroelastic monoclinic phase with space group P2(1)/n, a'=6.3072(3) angstrom, b'=6.3028(3) angstrom, c'=8.9882(3) angstrom, beta'=90.242(2)degrees, V=357.30(3) angstrom(3), Z =2, and D-x=3.383 g/cm(3). The low-temperature structure at 113 K was refined over 28 parameters,P to R-wp=20.9%, R-p=21.3%, R-exp= 12.5%, and R-B=6.93% from 453 independent reflections. (C) 2007 International Centre for Diffraction Data.
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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) : 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) : Vasil'ev A. D., Kocharova A. G.
Заглавие : Crystal structures of room- and low-temperature phases in oxyfluoride (N H4) 2 KW O3 F3
Место публикации : Powder Diffraction: International Centre For Diffraction Data, 2007. - Т. 22, № 3. - С. 227-230. - ISSN 0885-7156, DOI 10.1154/1.2759491
РИНЦ
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10.

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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11.

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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12.

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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13.

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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14.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Bogdanov E. V., Gorev M. V., Fokina V. D., Pogoreltsev E. I., Bondarev V. S., Flerov I. N., Laptash N. M.
Заглавие : Thermal properties and phase transitions in oxyfluoride (NH4)2NbOf5
Коллективы : Воронежский государственный технический университет, Российская академия наук, International Seminar on ferroelastic physics (6; 2009 ; Sept. 22-25; Voronezh), Международный семинар по физике сегнетоэластиков (6(11); 2009 ; 22-25 сент.; Воронеж)
Место публикации : The 6th International Seminar on Ferroelastic Physics: abstract book. - Voronezh, 2009. - P.26
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mel'nikova S. V., Krylov A. S., Zhogal' A. L., Laptash N. M.
Заглавие : Optical studies of phase transitions in the (NH4)(3)Ti(O-2)F-5 crystal
Коллективы : Russian Federation [NSh-1011.2008.2]; Russian Foundation for Basic Research [06-02-16102]; RFBR Enisei [07-02-096800]
Разночтения заглавия :авие SCOPUS: Optical studies of phase transitions in the (NH4) 3Ti(O2)F5 crystal
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2009. - Vol. 51, Is. 4. - P817-822. - ISSN 1063-7834, DOI 10.1134/S1063783409040301
Примечания : Cited References: 13. - This work was supported by the Council on Grants from the President of the Russian Federation (project no. NSh-1011.2008.2), the Russian Foundation for Basic Research (project no. 06-02-16102), and RFBR Enisei (project no. 07-02-096800).
Предметные рубрики: (NH4)(3)WO3F3 OXYFLUORIDE
RAMAN-SCATTERING
DISORDER
Аннотация: Polarization-optical study of twinning and measurements of the Raman spectra and birefringence in oxyfluoride (NH4)(3)Ti(O-2)F-5 were carried out over the temperature range 90-350 K. Phase transitions were detected at temperatures T (01) = 266 K (second-order transition) and T (02) = 225 K (first order). It is assumed that the crystal symmetry is changed as follows: Fm3m a dagger" I4/mmm a dagger" I4/m. Anomalies of the spectral parameters are established in the frequency range of internal vibrations of ammonium ions and Ti(O-2)F-5 complexes. An analysis of the results shows that the transition at T (01) is likely due to small shifts of the tetrahedral groups from their position on the triad axis and that the transition at T (02) is due to fluorine-oxygen ordering of Ti(O-2)F-5 complexes.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Smirnov L. S., Kolesnikov A. I., Flerov I. N., Laptash N. M.
Заглавие : Inelastic neutron scattering study of the specific features of the phase transitions in (NH4)(2)WO2F4
Коллективы : Russian Foundation [09-02-00062]; U.S. Department of Energy [DE-AC05-00OR22725, DE-AC02-06CH11357]
Место публикации : Phys. Solid State. - 2009. - Vol. 51, Is. 11. - P.2362-2366. - ISSN 1063-7834, DOI 10.1134/S1063783409110262
Примечания : Cited References: 15. - This study was supported by the Russian Foundation for Basic Research (project no. 09-02-00062) and the ORNL/SNS controlled by UT-Battelle, LLC, the U.S. Department of Energy (contract DE-AC05-00OR22725); the experiments in the Argonne National Laboratory were supported by the Office of General Sciences on Energy, Division of Materials Science of the U.S. Department of Energy (contract DE-AC02-06CH11357).
Предметные рубрики: OXYFLUORIDE
(NH4)(3)WO3F3
MECHANISM
RB
CS
Аннотация: Oxyfluoride (NH4)(2)WO2F4 has been studied by the inelastic neutron scattering method over a wide temperature range 10-300 K at two initial neutron energies of 15 and 60 meV. The role of tetrahedral ammonium groups in the mechanism of sequential phase transitions at T (1) = 201 K and T (2) = 160 K has been discussed.
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17.

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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18.

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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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Atuchin V. V., Gavrilova T. A., Kesler V. G., Molokeev M. S., Aleksandrov K. S.
Заглавие : Structural and electronic parameters of ferroelectric K3WO3F3
Коллективы :
Место публикации : Solid State Commun. - 2010. - Vol. 150, Is. 43-44. - P.2085-2088. - ISSN 0038-1098, DOI 10.1016/j.ssc.2010.09.023
Примечания : Cited References: 34. - This study was partly supported by RFBR (Grant 09-02-00062) and SB RAS (Grant 34).
Предметные рубрики: CORE-LEVEL SPECTROSCOPY
PHASE-TRANSITIONS
RHEED ANALYSIS
SURFACE
OXYFLUORIDE
ELPASOLITE
(NH4)(2)KWO3F3
SUBSTITUTION
TEMPERATURE
DIFFRACTION
Ключевые слова (''Своб.индексиров.''): ferroelectrics--chemical synthesis--electronic structure--photoelectron spectroscopies
Аннотация: The low-temperature ferroelectric G2 polymorph of K3WO3F3 oxyfluoride is formed by chemical synthesis. The electronic parameters of G2-K3WO3F3 have been measured by X-ray photoelectron spectroscopy under excitation with Al K alpha radiation (1486.6 eV). Detailed spectra have been recorded for all element core levels and Auger lines. The chemical bonding effects in the WO3 F-3 and WO6 octahedrons are considered by using the binding energy difference Delta BE(O-W) = BE(O 1s) BE(W 4f(7/2)). (C) 2010 Elsevier Ltd. All rights reserved.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mel'nikova S. V., Laptash N. M., Aleksandrov K. S.
Заглавие : Optical studies of phase transitions in oxyfluoride (NH4)(2)NbOF5
Место публикации : Phys. Solid State. - 2010. - Vol. 52, Is. 10. - P.2168-2172. - ISSN 1063-7834, DOI 10.1134/S1063783410100240
Примечания : Cited References: 6. - This study was supported by the Council on Grants from the President of the Russian Federation (grant no. NSh 4645.2010.2), the Russian Foundation for Basic Research (project no. 09-02-00062), and the Siberian Branch of the Russian Academy of Sciences (Integration Project no. 101).
Предметные рубрики: (NH4)(2)MOO2F4
Аннотация: Polarization-optical studies and measurements of the birefringence Delta n and the angle of rotation of the optical indicatrix for the (NH4)(2)NbOF5 crystal have been carried out in the temperature range 100-350 K. Two anomalies of the birefringence have been revealed at the temperatures T (01) = 258 K and T (02) a parts per thousand 219 K. According to the twinning pattern, the crystal undergoes successive changes in symmetry: orthorhombic a dagger" monoclinic 1 a dagger" monoclinic 2. The twofold axis of the monoclinic phases (or the normal to the plane) is directed along [001](or). The effect of the uniaxial compression along [011](or) and the electric field E a parts per thousand 25 kV/cm along [100](or) on the twin structure has been studied. The ferroelastic phase transition at T (01) is due to the appearance of the shear deformation x (4)(T) and is accompanied by significant anomalies of the birefringence. Strong pretransition phenomena mask the jumps in the birefringence Delta n(T) and in the angle of rotation of the indicatrix phi(T) at T (01).
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