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1.


    Melnikova, S. V.
    The role of structural and nonstructural water in oxyfluoride K2WO2F4 center dot H2O / S. V. Melnikova, A. D. Vasilev, A. G. Kocharova // Phys. Solid State. - 2011. - Vol. 53, Is. 12. - P. 2435-2440, DOI 10.1134/S1063783411120146. - Cited References: 16. - This work was supported by the Presidential Grant of the Russian Federation NSh-4645.2010.2, by the Russian Foundation for Basic Research, project no. 09-02-00062, and by the Integration Project of the Siberian Branch of the Russian Academy of Sciences no. 101. . - ISSN 1063-7834
РУБ Physics, Condensed Matter
Рубрики:
PHASE-TRANSITIONS
   OXOPEROXOFLUORO COMPLEXES

   MO V

   CRYSTAL STRUCTURE

   OXOFLUORO

   (NH4)(2)NBOF5

   (NH4)(2)WO2F4

   MONOHYDRATE

   DISORDER

Аннотация: X-ray structural and polarization optical investigations have been performed, and birefringence and rotation angles of the optical indicatrix phi (b) and phi (c) of the K2WO2F4 center dot H2O crystal have been measured in the temperature range of 100-600 K. The structure and symmetry of compounds at room temperature have been refined. It has been established that the layered crystal K2WO2F4 center dot H2O can exist in two states (A and B) depending on the atmospheric humidity and undergoes the sequence of reversible and irreversible phase transformations G (3)↔ G (2)↣ G (1)↣ G (0). The sequences of changes in the phase symmetry P (1) over bar↔C2/m↣ {4/nmm for samples A and m↔ C2/m↣P4/nmm for samples B havve been found. The second older proper ferroelastic phase transition (P(1) over bar↔ C2/m) at T-03 = 2700-290 K (G (3)↔ G (2)) is accompanied by twinning and appearance of the shift deformation x (6). The crystal system of the substance for the B crystals remains invariable after the second-order phase transition G (3) a dagger" G (2). The irreversible first-order phase transition G (2)↣ G (1) occurs in a temperature range T (02) a parts per thousand 350-380 K; it is accompanied by the loss of the crystallization water, which then is reduced easily from the atmosphere for a day. The substance decomposes at T (01) approximate to 510 K (G (1)↣ G (0)). The distinction between the A and B crystals has been explained by the presence or absence of free water in interlayer spacings.

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Держатели документа:
[Melnikova, S. V.
Vasilev, A. D.
Kocharova, A. G.] Russian Acad Sci, LV Kirensky Phys Inst, Siberian Branch, Krasnoyarsk 660036, Russia
ИФ СО РАН
Kirensky Institute of Physics, Siberian Branch of the Russian Academy of Sciences, Akademgorodok 50, Krasnoyarsk 660036, Russian Federation

Доп.точки доступа:
Vasilev, A. D.; Kocharova, A. G.; Кочарова, Алла Георгиевна; Мельникова, Светлана Владимировна
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2.


   
    Effect of cation substitution in fluorine-oxygen molybdates (NH4)(2-x) A (x) MoO2F4 / E. V. Bogdanov [et al.] // Phys. Solid State. - 2011. - Vol. 53, Is. 2. - P. 303-308, DOI 10.1134/S1063783411020065. - 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). . - ISSN 1063-7834
РУБ Physics, Condensed Matter
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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Держатели документа:
[Bogdanov, E. V.
Vasil'ev, A. D.
Flerov, I. N.] Russian Acad Sci, LV Kirensky Phys Inst, Siberian Branch, Krasnoyarsk 660036, Russia
[Vasil'ev, A. D.
Flerov, I. N.] Siberian Fed Univ, Inst Engn Phys & Radioelect, Krasnoyarsk 660074, Russia
[Laptash, N. M.] Russian Acad Sci, Inst Chem, Far Eastern Branch, Vladivostok 690022, Russia
ИФ СО РАН
Kirensky Institute of Physics, Siberian Branch, Russian Academy of Sciences, Akademgorodok, Krasnoyarsk 660036, Russian Federation
Institute of Engineering Physics and Radioelectronics, Siberian Federal University, ul. Kirenskogo 28, Krasnoyarsk 660074, Russian Federation
Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, pr. Stoletiya Vladivostoka 159, Vladivostok 690022, Russian Federation

Доп.точки доступа:
Bogdanov, E. V.; Богданов, Евгений Витальевич; Vasil'ev, A. D.; Васильев, Александр Дмитриевич; Flerov, I. N.; Флёров, Игорь Николаевич; Laptash, N. M.
}
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3.


   
    Phase transitions in the (NH4)(2)NbOF5 oxyfluoride / V. D. Fokina [et al.] // Phys. Solid State. - 2010. - Vol. 52, Is. 4. - P. 781-788, DOI 10.1134/S1063783410040189. - 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). . - ISSN 1063-7834
РУБ Physics, Condensed Matter
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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Держатели документа:
[Fokina, V. D.
Bogdanov, E. V.
Gorev, M. V.
Molokeev, M. S.
Flerov, I. N.] Russian Acad Sci, Siberian Branch, LV Kirensky Phys Inst, Krasnoyarsk 660036, Russia
[Fokina, V. D.
Gorev, M. V.
Pogorel'tsev, E. I.
Flerov, I. N.] Siberian Fed Univ, Krasnoyarsk 660041, Russia
[Laptash, N. M.] Russian Acad Sci, Far Eastern Branch, Inst Chem, Vladivostok 690022, Russia
ИФ СО РАН
Kirensky Institute of Physics, Siberian Branch, Russian Academy of Sciences, Akademgorodok 50, Krasnoyarsk 660036, Russian Federation
Siberian Federal University, pr. Svobodny 79, Krasnoyarsk 660041, Russian Federation
Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, pr. Stoletiya Vladivostoka 159, Vladivostok 690022, Russian Federation

Доп.точки доступа:
Fokina, V. D.; Фокина, Валентина Дмитриевна; Bogdanov, E. V.; Богданов, Евгений Витальевич; Gorev, M. V.; Горев, Михаил Васильевич; Molokeev, M. S.; Молокеев, Максим Сергеевич; Pogorel'tsev, E. I.; Flerov, I. N.; Флёров, Игорь Николаевич; Laptash, N. M.
}
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4.


   
    Calorimetric and dielectric studies of the (NH4)(2)MoO2F4 oxyfluoride / V. D. Fokina [et al.] // Phys. Solid State. - 2010. - Vol. 52, Is. 1. - P. 158-166, DOI 10.1134/S1063783410010282. - Cited References: 22. - This study was supported by the Russian Foundation for Basic Research ( project no. 09-02-00062). . - ISSN 1063-7834
РУБ Physics, Condensed Matter
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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Держатели документа:
[Fokina, V. D.
Bogdanov, E. V.
Bondarev, V. S.
Flerov, I. N.] Russian Acad Sci, Siberian Branch, LV Kirensky Phys Inst, Krasnoyarsk 660036, Russia
[Fokina, V. D.
Pogorel'tsev, E. I.
Bondarev, V. S.
Flerov, I. N.] Siberian Fed Univ, Krasnoyarsk 660041, Russia
[Laptash, N. M.] Russian Acad Sci, Far Eastern Branch, Inst Chem, Vladivostok 690022, Russia
ИФ СО РАН
Kirensky Institute of Physics, Siberian Branch, Russian Academy of Sciences, Akademgorodok 50, Krasnoyarsk 660036, Russian Federation
Siberian Federal University, pr. Svobody 79, Krasnoyarsk 660041, Russian Federation
Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, pr. Stoletiya Vladivostoka 159, Vladivostok 690022, Russian Federation

Доп.точки доступа:
Fokina, V. D.; Фокина, Валентина Дмитриевна; Bogdanov, E. V.; Богданов, Евгений Витальевич; Pogorel'tsev, E. I.; Bondarev, V. S.; Бондарев, Виталий Сергеевич; Flerov, I. N.; Флёров, Игорь Николаевич; Laptash, N. M.
}
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5.


    Mel'nikova, S. V.
    Phase transitions in orthorhombic oxyfluoride (NH4)(2)MoO2F4 / S. V. Mel'nikova, N. M. Laptash // Phys. Solid State. - 2008. - Vol. 50, Is. 3. - P. 511-514, DOI 10.1134/S1063783408030207. - Cited References: 15 . - ISSN 1063-7834
РУБ Physics, Condensed Matter
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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Держатели документа:
[Mel'nikova, S. V.] Russian Acad Sci, LV Kirensky Phys Inst, Siberian Branch, Krasnoyarsk 660036, Russia
[Laptash, N. M.] Russian Acad Sci, Inst Chem, Far E Div, Vladivostok 690022, Russia
ИФ СО РАН

Доп.точки доступа:
Laptash, N. M.; Мельникова, Светлана Владимировна
}
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6.


   
    Mechanism and nature of phase transitions in the (NH4)(3)MoO3F3 oxyfluoride / I. N. Flerov [et al.] // Phys. Solid State. - 2008. - Vol. 50, Is. 3. - P. 515-524, DOI 10.1134/S1063783408030219. - Cited References: 13 . - ISSN 1063-7834
РУБ Physics, Condensed Matter
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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Держатели документа:
[Flerov, I. N.
Fokina, V. D.
Bovina, A. F.
Bogdanov, E. V.
Molokeev, M. S.
Kocharova, A. G.] Russian Acad Sci, LV Kirensky Phys Inst, Siberian Branch, Krasnoyarsk 660036, Russia
[Pogorel'tsev, E. I.] Siberian Fed Univ, Polytech Inst, Krasnoyarsk 660074, Russia
[Laptash, N. M.] Russian Acad Sci, Inst Chem, Far E Div, Vladivostok 690022, Russia
ИФ СО РАН

Доп.точки доступа:
Flerov, I. N.; Флёров, Игорь Николаевич; Fokina, V. D.; Фокина, Валентина Дмитриевна; Bovina, A. F.; Бовина, Ася Федоровна; Bogdanov, E. V.; Богданов, Евгений Витальевич; Molokeev, M. S.; Молокеев, Максим Сергеевич; Kocharova, A. G.; Кочарова, Алла Георгиевна; Pogorel'tsev, E. I.; Laptash, N. M.
}
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