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Общее количество найденных документов : 103
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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrova I.P., Ivanov Yu.N., Bondarev V.S., Sukhovskiy A.A., Voronov V.N.
Заглавие : Calorimetric and 23Na MAS NMR Study of the Phase Diagram of NaNb1-xTaxO3 Solid Solutions
Место публикации : Functional mate rials. - 2010. - Vol. 17. - С. 18-24
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrova I. P., Ivanov Y. N., Bondarev V. S., Sukhovskii A. A., Voronov V. N.
Заглавие : Calorimetric and 23Na MAS NMR study of the phase diagram of NANB1_xTAxO3 solid solutions
Место публикации : Functional Materials. - 2010. - Vol. 17, Is. 1. - P.18-23. - ISSN 1027-5495
Аннотация: The heat capacity of NaNb1_xTaxO3 solid solutions was measured in the temperature range 100 to 770 K. The step-like change of phase transition temperature is observed in the T-x phase diagram at concentration x = 0.55. The obtained results are in a good agreement with the data of dielectric studies. The 23Na MAS NMR spectra were obtained at Larmor frequency 79.35 MHz using a Bruker AVANCE 300 spectrometer. The quadru-polar coupling constant, (CQ=e2qQ/h) and asymmetry parameter (n) were determined by computer fitting of the NMR line shape using the DMFit software. The found parameters show that solid solution structure is NaTa03-based at 0.7<X ?1 and NaNbO3-based at 0?x?0.5. The spectra in the intermediate region (0.5<x?0.7) can be described at a reasonable accuracy when assuming the coexistence of NaTaO3 and NaNbO3 structures. В© 2010 - STC "Institute for Single Crystals".
Scopus
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ivanov Y. N., Totz J., Michel D., Klotzsche G., Sukhovsky A. A., Aleksandrova I. P.
Заглавие : Chemical exchange in NH4HSeO4 single crystals studied by two-dimensional H-2 nuclear magnetic resonance
Разночтения заглавия :авие SCOPUS: Chemical exchange in NH4HSeO4 single crystals studied by two-dimensional 2H nuclear magnetic resonance
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 1999. - Vol. 11, Is. 18. - P.3751-3760. - ISSN 0953-8984, DOI 10.1088/0953-8984/11/18/310
Примечания : Cited References: 16
Предметные рубрики: PHASE-TRANSITIONS
CONDUCTIVITY PROCESSES
AMMONIUM
Ключевые слова (''Своб.индексиров.''): hydrogen bonds--nuclear magnetic resonance--single crystals--thermal effects--ammonium hydrogen selenate--ammonium compounds
Аннотация: Processes of chemical exchange of deuterons in partially deuterated ammonium hydrogen selenate, NH4HSeO4 (AHSe), crystals are investigated by means of H-2 nuclear magnetic resonance (NMR) experiments over a wide temperature range. The temperature dependencies of the quadrupole line splittings in the one-dimensional spectra of AHSe above 350 K revealed lineshape changes which are characteristic for chemical exchange processes. A detailed study of these exchange processes in AHSe is achieved by means of two-dimensional H-2 NMR experiments. In the temperature range investigated, a chemical exchange occurs only between those deuteron (proton) sites which are involved in hydrogen bonds (alpha- and beta-positions). It was established that the rates of exchange between all types of hydrogen-bound deuteron are approximately the same. Exchange between these positions and the deuterons in the ND4 groups could not be detected. On the basis of our findings, we finally discuss a model for the microscopic mechanism of hydrogen transport in AHSe.
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrova I. P., Rosanov O. V., Sukhovsky A. A., Moskvich Y. N.
Заглавие : Detection of the incommensurate modulation of the hydrogen-bond double-minimum potential in the antiferroelectric phase of NH4HSEO4
Место публикации : Phys. Lett. A. - 1983. - Vol. 95, Is. 6. - P.339-342. - ISSN 0375-9601, DOI 10.1016/0375-9601(83)90035-X
Примечания : Cited References: 15
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrova I. P., Seryukova I. V., Zherebtsova L. I.
Заглавие : Dielectric permittivity behavior at nonequilibrium processes in nh4hseo4 ferroelectrics
Место публикации : Fiz. Tverd. Tela. - 1985. - Vol. 27, Is. 11. - P.3438-3441. - ISSN 0367-3294
Примечания : Cited References: 5
WOS
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrova I. P., Moskvich Yu. N., Rozanov O. V., Sadreev A. F., Sukhovskii A. A.
Заглавие : Dislocation instability of an incommensurate phase in connection with the floating phase in an NH4HSeO4 crystal
Место публикации : JETP Letters. - 1984. - Vol. 40, Is. 4. - P.879-881. - ISSN 0021-3640
Примечания : Cited References: 7
WOS
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrova I. P., Moskvich Yu. N., Rozanov O. V., Sukhovsky A. A.
Заглавие : Dislocations and time-dependent dynamics of the incommensurate phase of NH4HSEO4
Место публикации : Ferroelectr. Lett. Sect. - 1984. - Vol. 1, Is. 5-6. - P.131-134. - ISSN 0731-5171, DOI 10.1080/07315178408202410
Примечания : Cited References: 5
WOS
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Popov M. A., Aleksandrova I. P., Primak S. V.
Заглавие : Effect of fluctuations on the NQR spectrum in the incommensurate phase of a Cs2ZnI4 crystal
Место публикации : JETP Letters. - 1994. - Vol. 59, Is. 7. - P.485-487. - ISSN 0021-3640
Примечания : Cited References: 5
Аннотация: The direct spin-lattice relaxation due to local thermal fluctuations of the amplitude of the atomic-displacement wave -in the incommensurate phase of a crystal can strongly influence the lineshape of the resonant spectrum, reducing the intensity of the outermost temperature-dependent peaks in the frequency distribution, while having essentially no effect on the temperature-independent features of this distribution. This effect is apparently the reason for the anomalous behavior of the NQR spectrum of I-127 in Cs2ZnI4 in a certain temperature interval near the transition from the ''normal'' phase to the incommensurate phase.
WOS
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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : PARLINSKI K., CURRAT R., VETTIER C., ALEKSANDROVA I. P., ECKOLD G.
Заглавие : Effect of hydrostatic-pressure on modulated phases in Rb2ZnBr4
Разночтения заглавия :авие SCOPUS: Effect of hydrostatic pressure on modulated phases in Rb2ZnBr4
Место публикации : Phys. Rev. B. - 1992. - Vol. 46, Is. 1. - P.106-114. - ISSN 0163-1829, DOI 10.1103/PhysRevB.46.106
Примечания : Cited References: 36
Предметные рубрики: INCOMMENSURATE PHASES
NEUTRON-SCATTERING
X-RAY
COMMENSURATE
TRANSITIONS
EVOLUTION
MODEL
WAVE
Аннотация: Neutron-diffraction studies on modulated Rb2ZnBr4, carried out under hydrostatic pressure, revealed two new commensurate phases characterized by wave vectors q = 2/7b* and q = 1/4b*, respectively. The first order phase transition between them is revealed by the coexistence of two distinct peaks in the diffraction pattern. The observed pressure-temperature phase diagram contains: the above-mentioned phases, the ferroelectric commensurate phase q = 1/3, and a region characterized by wave-vector values in the interval q = 2/7-1/3. In this region the modulation wave vector exhibits stepwise behavior as a function of pressure, but remains nearly constant iii temperature runs. We have found in this region a characteristic memory effect in which two temperature runs performed at the same pressure lead to two different modulation wave-vector values, while only the thermal history of the sample is different in the two runs. At ambient pressure we confirm the presence of a multipeaked diffraction pattern just above the lock-in transition to the commensurate q = 1/3 phase. At 122 K the phase transition from the 1/3 phase to the 1/4 phase is detected in pressure scans. The transition mechanism involves the q = 2/7 phase, at least as a metastable intermediate phase.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrova I. P., Bartolome J., Falvello L. R., Torres J. M., Sukhovskii A. A.
Заглавие : Effect of impurities on the successive phase transitions in (Cs1-xRbx)(2)ZnI4 compounds
Разночтения заглавия :авие SCOPUS: Effect of impurities on the successive phase transitions in (Cs1-xRbx)2ZnI4 compounds
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2002. - Vol. 14, Is. 49. - P.13623-13634. - ISSN 0953-8984, DOI 10.1088/0953-8984/14/49/316
Примечания : Cited References: 27
Предметные рубрики: X-RAY
CS2ZNI4
SYSTEM
HEAT
Ключевые слова (''Своб.индексиров.''): phase transitions--point defects--specific heat--temperature--x ray diffraction analysis--zinc compounds--lock-in transition--nuclear quadrupole resonance--single crystals
Аннотация: The heat capacity, nuclear quadrupole resonance (NQR) and x-ray diffraction of (Cs1-xRbx)(2)ZnI4 single crystals have been measured, for x = 0, 0.001, 0.005, 0.01, 0.025 and 0.05. The normal to incommensurate (N-Inc) phase transition at T-I, the incommensurate to commensurate (Inc-C) lock-in transition at T-L and the structural commensurate monoclinic to triclinic transition at T-LT, observed in the parent compound (x = 0), takes place for x = 0, 0.001, 0.005 and 0.01. For x = 0.025 only T-I and T-L are detected, while for x = 0.05 no transitions were observable. The values of T-I and T-L increase with x while T-LT decreases and disappears at the concentration x = 0.025. The effect of defects, besides modifying the transition temperatures, is that of broadening and lowering the heat capacity anomaly at the lock-in transition until its total quenching for x = 0.05. No observable hysteresis is detected in this transition. NQR and x-ray diffraction data show the Inc-C transition up to the highest concentration. We conclude that this phenomenology is caused by weak interaction of the incommensurate modulation with point defects even in the region close to the Inc-C transition.
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