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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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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrov K. S.
Заглавие : Phase-transitions and distortions of the structure in the family of crystals related to alpha-k2so
Место публикации : Kristallografiya. - 1993. - Vol. 38, Is. 1. - P.128-139. - ISSN 0023-4761; Crystallogr. Rep.
Примечания : Cited References: 38
Предметные рубрики: X-RAY
EXPECTED STRUCTURES
A2BX4 COMPOUNDS
TEMPERATURE
(NH4)2BEF4
CHEMISTRY
DISORDER
SYMMETRY
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrov K. S., Beznosikov B. V.
Заглавие : Hierarchies of perovskite-like crystals (Review)
Место публикации : Phys. Solid State: AMER INST PHYSICS, 1997. - Vol. 39, Is. 5. - P.695-715. - ISSN 1063-7834, DOI 10.1134/1.1130120
Примечания : Cited References: 143
Предметные рубрики: CU-O SYSTEM
HIGH-PRESSURE SYNTHESIS
SUPERCONDUCTING COPPER OXIDES
STRUCTURAL PHASE-TRANSITIONS
NEUTRON POWDER DIFFRACTION
SINGLE-CRYSTAL
X-RAY
CUPRATE SUPERCONDUCTORS
DIELECTRIC-PROPERTIES
HOMOLOGOUS SERIES
Аннотация: A system of mutual relationships (a hierarchy) is constructed between various perovskite-like crystal structures based on available structural data. All the perovskite-like structures are characterized by a common indicator of their relationship-the presence of layers, stacks, or frameworks made up of BX6 octahedra linked at their vertices (where B is a cation, X is an anion) or fragments of octahedra in the form of BX5 pyramids or BX4 squares in anion-deficient compounds. In layered structures, these stacks are joined to each other by various intermediate blocks. It is well known that one homological series of compounds is constructed by increasing the number of layers in a stack while preserving the same kind of connecting block. Crystals of various series that contain identical stacks (but different blocks of one or two types) can also be related to one another via this feature. The hierarchical system includes compounds with small distortions in their structures for various reasons. (C) 1997 American Institute of Physics.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrov K. S., Bartolome J., Gorev M. V., Flerov I. N.
Заглавие : Hydrostatic pressure effect on phase transitions in perovskites with ammonium cations
Место публикации : Phys. Status Solidi B. - 2000. - Vol. 217, Is. 2. - P.785-791. - ISSN 0370-1972, DOI 10.1002/(SICI)1521-3951(200002)217:2785::AID-PSSB7853.0.CO;2-Y
Примечания : Cited References: 36
Предметные рубрики: XMF3 CUBIC PEROVSKITES
THERMAL-PROPERTIES
HEAT-CAPACITY
TEMPERATURE DEPENDENCE
DIELECTRIC PROPERTIES
X-RAY
NH4ZNF3
NH4MNCL3
NH4COF3
NH4CDF3
Аннотация: The pressure dependence of the structural phase transition temperature has been measured for the powder samples of NH4MgF3, NH4ZnF3, NH4MnF3, NH4CoF3, NH4CdF3, and NH4MnCl3 perovskites in the pressure range 0 to 600 MPa. It was found that the values of dT(0)/dP are negative for the Mg, Zn. Co. Mn trifluorides and positive for NH4CdF3 and NH4MnCl3. Comparison with the known data for other halide and oxide perovskites allowed to conclude that the sign of dT(0)/dP is correlated with the value of the Goldschmidt tolerance factor of the perovskite, and its value is closely related to the temperature and mechanism of the transition.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Gorev M. V., Sciau P.
Заглавие : Heat capacity and p-T phase diagrams of the ordered perovskites Pb2MgWO6 and Pb2CoWO6
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2000. - Vol. 12, Is. 5. - P.559-567. - ISSN 0953-8984, DOI 10.1088/0953-8984/12/5/304
Примечания : Cited References: 25
Предметные рубрики: CRYSTAL-STRUCTURE
X-RAY
TRANSITIONS
PRESSURE
Аннотация: The heat capacities of Pb2MgWO6 and Pb2CoWO6 and the effect of hydrostatic pressure on the phase transitions have been studied on powdered samples by means of an adiabatic calorimeter and DTA performed under pressure, respectively. Thermodynamic parameters, such as change of total excess entropy, latent hear and hysteresis of the phase transition temperature were determined. Entropies and p-T phase diagrams are discussed in connection with structural data.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrov K. S., Bartolome J.
Заглавие : Structural distortions in families of perovskite-like crystals
Место публикации : Phase Transit.: TAYLOR & FRANCIS LTD, 2001. - Vol. 74, Is. 3. - P.255-335. - ISSN 0141-1594, DOI 10.1080/01411590108228754
Примечания : Cited References: 262
Предметные рубрики: LOW-TEMPERATURE PHASE
INELASTIC-NEUTRON-SCATTERING
POWDER PROFILE REFINEMENT
MII = CO
X-RAY
RAMAN-SCATTERING
ORDERED PEROVSKITE
RHOMBOHEDRAL PEROVSKITES
RB2KMIIIF6 ELPASOLITES
MAGNETIC-PROPERTIES
Ключевые слова (''Своб.индексиров.''): structural phase transitions--perovskites--perovskite-like crystals--group theoretical classification
Аннотация: The crystallographic and group theoretical analysis of the structural phase transitions in perovskite and perovskite-like crystals is reviewed. We include ABX(3) perovskites and their relative crystals of ReO3 type (G(0) = O-h(1)), elpasolites, cryolites and their relatives (G(0) = O-h(5)) layered crystals of TIAIF(4) series (G(0) = D-4h(1)), Aurivillius and Ruddlesden-Popper series (G(0) = D-4h(17)). The structures in their initial phase G(0) often contain n layers (n = 1, 2,3) of vertex linked octahedra. The distorted phases produced by one kind of tilt and by superposition of tilts in the slabs are enumerated. Most of the tilts correspond to symmetry changes, which can be associated to definite librational lattice modes irreducible representations of the G(0) group. The softening of modes associated to the PT has been found experimentally in many perovskites, elpasolites and layered crystals with n = 1. In contrast, no such soft modes have been found yet for even-layered (n = 2) crystals. Examples of successive phase transitions due to the superposition of tilts in these types of crystals have been collected.
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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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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mel'nikova S. V., Isaenko L. I., Pashkov V. M., Pevnev I. V.
Заглавие : Phase transition in a KPb2Br5 crystal
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2005. - Vol. 47, Is. 2. - P332-336. - ISSN 1063-7834, DOI 10.1134/1.1866415
Примечания : Cited References: 5
Предметные рубрики: CSLICRO4 CRYSTAL
X-RAY
Аннотация: Crystals of the KPb2Br5 compound are investigated using polarized light microscopy and calorimetry. The birefringence and the angle of rotation of the optical indicatrix are measured in the temperature range 270-620 K. It is found that the KPb2Br5 crystal undergoes a first-order ferroelastic phase transition at temperatures T-0up arrow = 519.5 K and T-0down arrow = 518.5 K with a change in the enthalpy DeltaH = 1300 +/- 200 J/mol. This transition is accompanied by both twinning and the symmetry change mmm P2(l)/c. It is revealed that the angle of rotation of the optical indicatrix exhibits an unusual behavior under variations in the temperature due to a strong temperature dependence of the birefringence. (C) 2005 Pleiades Publishing, Inc.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mel'nikova S. V., Voronov V. N.
Заглавие : Specific features of the ferroelastic phase transition in CsLiS1-zCrzO4 solid solutions
Разночтения заглавия :авие SCOPUS: Specific features of the ferroelastic phase transition in CsLiS 1-z CrzO4 solid solutions
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2006. - Vol. 48, Is. 9. - P1786-1790. - ISSN 1063-7834, DOI 10.1134/S1063783406090290
Примечания : Cited References: 11
Предметные рубрики: CSLICRO4 CRYSTAL
X-RAY
CSLISO4
Аннотация: Single crystals of the CsLiS1-zCrzO4 solid solutions (z = 0, 0. 1, 0.4, 0.5, 0.9, 1.0) are grown, optical polarization studies are performed, and the birefringence and the angle of rotation of the optical indicatrix phi(T) are measured. A (z-T) phase diagram is constructed in the temperature range from 77 to similar to 550 K. It is established that substitution of chromium for sulfur has practically no effect on the shape of the optical indicatrix in the initial phase with Pmcn symmetry but produces strong distortions in the monoclinic phase with P112(1)/n symmetry. The unusual shape of the curve phi(T) for compositions with z approximate to 1 is accounted for by the interaction of the polarization-constant tensor components a(ij). No radical differences in the patterns of the ferroelastic phase transition between CsLiSO4 and CsLiCrO4 are revealed (the critical exponent for the transition parameter is beta = 0.33 +/- 0.01). These crystals differ only in the magnitudes of the anomalies, which is associated with the large difference between the ionic radii of sulfur and chromium.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Kartashev A. V., Mel'nikova S. V.
Заглавие : Calorimetric and optical studies of orthorhombic and cubic CsLiCrO4 crystals
Разночтения заглавия :авие SCOPUS: Calorimetric and optical studies of orthorhombic and cubic CsLiCrO 4 crystals
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2006. - Vol. 48, Is. 11. - P2171-2176. - ISSN 1063-7834, DOI 10.1134/S1063783406110242
Примечания : Cited References: 23
Предметные рубрики: PHASE-TRANSITIONS
X-RAY
NH4LISO4
ALPHA
Аннотация: Careful calorimetric and polarization optical studies of a metastable cubic modification of a CsLiCrO4 crystal (space group (F43m)) are performed. Anomalies of the heat capacity indicative of structural distortions at 92.4 and 69.1 K were revealed, and the values of the thermodynamic parameters of the phase transitions were determined. The crystal twinning in the intermediate phase was studied. A comparative analysis of the phase transitions occurring in a series of ALiMO(4) crystals (A=NH4, Cs; M=S, Cr, Mo, W) was performed. First studies of the monotropic structural transformation F43m - Pmcn and the enantiotropic phase transition Pmcn reversible arrow P112(1)/n were carried out using scanning calorimetry, and the thermodynamic parameters of these transitions were determined.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krylov A. S., Krylova S. N., Laptash N. M., Vtyurin A. N.
Заглавие : Raman scattering study of temperature induced phase transitions in crystalline ammonium heptafluorozirconate, (NH4)3ZrF7
Место публикации : Vib. Spectrosc.: Elsevier Science BV, 2012. - Vol. 62. - P.258-263. - ISSN 0924-2031, DOI 10.1016/j.vibspec.2012.07.003
Примечания : Cited References: 31. - This work was partly supported by integration project SB RAS No 28, Russian Foundation for Basic Research project No 11-02-98002-r_siberia, No 12-02-00056, SS-4828.2012.2. The authors are grateful to Dr. I.N. Flerov for helpful discussions. The assistance of Dr. S. Skokov is sincerely appreciated.
Предметные рубрики: VIBRATIONAL-SPECTRA
X-RAY
DISORDER
DIFFRACTION
ELPASOLITE
SYMMETRY
RB2KSCF6
IF7
Ключевые слова (''Своб.индексиров.''): raman spectroscopy--phase transition--ammonium heptafluorozirconate--low temperature
Аннотация: This paper reports on a Raman spectroscopy investigation of phase transitions in (NH4)3ZrF7 crystal. Raman spectra were obtained and analyzed in a wavenumber range from 3800 to 15 cm−1 and in the temperature range from 7 to 360 K. The anomalies caused by a series of subsequent structural phase transitions have been analyzed. A soft phonon mode restoring in the distorted phase was found. The spectral changes observed in the current study are similar to those typically found in phase transitions near a tricritical point. The spectral changes in the middle wavenumber range, 700–150 cm−1, indicate that the phase transitions are due to structural ordering of pentagonal ZrF73− bipyramids. Spectral data also show that a phase transition near 225 K is accompanied by an increase of the unit cell volume. In addition, spectral changes in the range of internal vibrations of ammonium ions indicate that the ion's motion slows down with decrease of temperature.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Likhacheva A. Y., Goryainov S. V., Krylov A. S., Bul'bak T. A., Prasad PSR
Заглавие : Raman spectroscopy of natural cordierite at high water pressure up to 5?GPa
Место публикации : J. Raman Spectrosc.: Wiley-Blackwell, 2012. - Vol. 43, Is. 4. - P.559-563. - ISSN 0377-0486, DOI 10.1002/jrs.3060
Примечания : Cited References: 38. - We greatly appreciate the critical comments of Prof. R. Kaindl and an anonymous reviewer on this work, and we thank Dr G. Lepezin for providing the cordierite sample. This work was supported by RFBR grant 11-05-01121-a.
Предметные рубрики: SINGLE-CRYSTAL STRUCTURE
X-RAY
CHANNEL H2O
BEHAVIOR
SPECTRA
CO2
POLYMORPHISM
DIFFRACTION
CHEMISTRY
CAVITIES
Ключевые слова (''Своб.индексиров.''): cordierite--raman spectroscopy--high pressure--phase transition
Аннотация: The high-pressure behaviour of cordierite, a widespread ring aluminosilicate with channels incorporating fluid compounds (H2O, CO2), is characterized by the absence of phase transitions up to 2.5 GPa. However, the distortion of the ring tetrahedra observed previously at 2.3 GPa is supposed to introduce a phase transition at higher pressure, which has not been checked so far. This work presents a high-pressure Raman spectroscopic study of natural cordierite compressed in water medium up to 4.7 GPa in a diamond anvil cell. At P 4 GPa, a disordering of both the framework and intrachannel H2O subsystem is apparent from significant broadening of Raman peaks and the evolution of short-range order parameters. This is followed by abrupt shifts of the framework and O–H stretching modes at about 4.5 GPa, indicating a first-order phase transition. Its reversibility is seen from the recovery of the initial spectrum at P 3 GPa. The shift amplitudes of different framework modes indicate the predominance of distortion over contraction of the framework polyhedra upon this transition. The disordering of the H2O subsystem in the high-pressure phase is likely a consequence of distortion of the channel-forming framework elements, which is supposed to be a driving force of this transition. Copyright © 2011 John Wiley & Sons, Ltd.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Atuchin V. V., Aleksandrovsky A. S., Chimitova O. D., Gavrilova T. A., Krylov A. S., Molokeev M. S., Oreshonkov A. S., Bazarov B. G., Bazarova J. G.
Заглавие : Synthesis and spectroscopic properties of monoclinic α-Eu2(MoO4)3
Коллективы : Ministry of Education and Science of the Russian Federation
Место публикации : J. Phys. Chem. C: American Chemical Society, 2014. - Vol. 118, Is. 28. - P.15404-15411. - ISSN 1932-7447, DOI 10.1021/jp5040739
Примечания : Cited References: 63. - This study is partly supported by the Ministry of Education and Science of the Russian Federation.
Предметные рубрики: RARE-EARTH MOLYBDATES
VIBRATIONAL PROPERTIES
LUMINESCENCE PROPERTIES
CRYSTAL-STRUCTURE
PHASE-TRANSITIONS
TRIPLE MOLYBDATE
SINGLE-CRYSTAL
X-RAY
PHOSPHORS
EUROPIUM
Аннотация: The microcrystals of monoclinic europium molybdate, alpha-Eu-2(MoO4)(3), have been fabricated by solid-state synthesis at T = 753-1273 K for 300 h. The crystal structure of alpha-Eu-2(MoO4)(3) has been refined by the Rietveld method and was found to belong to the space group C2/c with unit cell parameters a = 7.5576(1), b = 11.4709(2), c = 11.5158(2) angstrom, and beta = 109.278(1)degrees (R-B = 3.39%). About 40 narrow Raman lines have been observed in the Raman spectrum of the alpha-Eu-2(MoO4)(3) powder sample. The luminescence spectra of alpha-Eu-2(MoO4)(3) under excitation at 355 and 457.9 nm reveal domination of induced electric dipole transition D-5(0) - F-7(2) and the presence of ultranarrow lines at D-5(0) - F-7(0) and D-5(1) - F-7(0) transitions.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Myagkov V. G., Zhigalov V. S., Matsynin A. A., Bykova L. E., Mikhlin Y. L., Bondarenko G. N., Patrin G. S., Yurkin G. Yu.
Заглавие : Formation of ferromagnetic germanides by solid-state reactions in 20Ge/80Mn films
Место публикации : Thin Solid Films: Elsevier Science, 2014. - Vol. 552. - P.86-91. - ISSN 0040-6090, DOI 10.1016/j.tsf.2013.12.029
Примечания : Cited References: 53
Предметные рубрики: PHASE-FORMATION
MAGNETIC-PROPERTIES
Mn5Ge3 FILMS
X-RAY
Ge(111)
TRANSFORMATIONS
DIFFUSION
SPECTRA
SYSTEM
LAYERS
Ключевые слова (''Своб.индексиров.''): manganite-germanium--solid state reaction--first phase--mn5ge3 alloy--carbon impurity--oxygen impurity--annealing--magnetic anisotropy
Аннотация: Solid state reactions between Ge and Mn films are systematically examined using X-ray diffraction, photoelectron spectroscopy, and magnetic and electrical measurements. The films have a nominal atomic ratio Ge:Mn = 20:80 and are investigated at temperatures from 50 to 500 °C. It is established that after annealing at ~ 120°C, the ferromagnetic Mn5Ge3 phase is the first phase to form at the 20Ge/80Mn interface. As the annealing temperature increases to 300°C, the weak magnetic Mn5Ge 2 + Mn3Ge phases simultaneously begin to grow and they become dominant at 400°C. Increasing the annealing temperature to 500°C leads to the formation of the ferromagnetic phase with a Curie temperature TC ~ 350-360 K and magnetization 14-25 kA/m at room temperature. The X-ray diffraction study of the samples shows the reflections from the Mn 5Ge3 phase, and the photoelectron spectra contain the oxygen and carbon peaks. The homogeneous distribution of oxygen and carbon over the sample thickness suggests that the increased Curie temperature and magnetization are related to the migration of C and O atoms into the Mn 5Ge3 lattice and the formation of the Nowotny phase Mn5Ge3CxOy. The initiation temperature (~ 120 C) is the same in the Mn5Ge3 phase with the solid-state reactions in the Ge/Mn films as well as in the phase separation in the GexMn1 - x diluted semiconductors. Thus, we conclude that the synthesis of the Mn5Ge3 phase is the moving force for the spinodal decomposition of the GexMn 1 - x diluted semiconductors.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Myagkov V. G., Bayukov O. A., Mikhlin Y. L., Zhigalov V. S., Bykova L. E., Bondarenko G. N.
Заглавие : Long-range chemical interactions in solid-state reactions: effect of an inert Ag interlayer on the formation of L10-FePd in epitaxial Pd(0 0 1)/Ag(0 0 1)/Fe(0 0 1) and Fe(0 0 1)/Ag(0 0 1)/Pd(0 0 1) trilayers
Место публикации : Philos. Mag.: Taylor & Francis, 2014. - Vol. 94, Is. 23. - P.2595-2622. - ISSN 1478-6435, DOI 10.1080/14786435.2014.926037. - ISSN 1478-6443
Примечания : Cited References: 117
Предметные рубрики: HIGH-TEMPERATURE SYNTHESIS
THIN-FILMS
PHASE-FORMATION
MAGNETIC-PROPERTIES
X-RAY
MARTENSITIC TRANSFORMATIONS
PHOTOELECTRON-SPECTROSCOPY
STRUCTURAL CHARACTERISTICS
CASIMIR FORCE
GOLD-FILMS
Ключевые слова (''Своб.индексиров.''): fe-pd system--epitaxial thin film--inert ag buffer layer--diffusion--solid-state reactions--l1(0)--long-range chemical interactions
Аннотация: The effect of 0, 0.5, and 1 μm-thick Ag interlayers on the chemical interaction between Pd and Fe in epitaxial Pd(0 0 1)/Ag(0 0 1)/Fe(0 0 1)/MgO(0 0 1) and Fe(0 0 1)/Ag(0 0 1)/Pd(0 0 1)/MgO(0 0 1) trilayers has been studied using X-ray diffraction, 57Fe Mössbauer spectroscopy, X-ray photoelectron spectroscopy, and magnetic structural measurements. No mixing of Pd and Fe occurs via the chemically inert Ag layer at annealing temperatures up to 400 °C. As the annealing temperature is increased above 400 °C, a solid-state synthesis of an ordered L10-FePd phase begins in the Pd(0 0 1)/Ag(0 0 1)/Fe(0 0 1) and Fe(0 0 1)/Ag(0 0 1)/Pd(0 0 1) film trilayers regardless of the thickness of the buffer Ag layer. In all samples, annealing above 500 °C leads to the formation of a disordered FexPd1−x(0 0 1) phase; however, in samples lacking the Ag layer, the synthesis of FexPd1−x is preceded by the formation of an ordered L12-FePd3 phase. An analysis of the X-ray photoelectron spectroscopy results shows that Pd is the dominant moving species in the reaction between Pd and Fe. According to the preliminary results, the 2.2 μm-thick Ag film does not prevent the synthesis of the L10-FePd phase and only slightly increases the phase’s initiation temperature. Data showing the ultra-fast transport of Pd atoms via thick inert Ag layers are interpreted as direct evidence of the long-range character of the chemical interaction between Pd and Fe. Thus, in the reaction state, Pd and Fe interact chemically even though the distance between them is about 104 times greater than an ordinary chemical bond length.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Atuchin V. V., Aleksandrovsky A. S., Chimitova O. D., Diao C. P., Gavrilova T. A., Kesler V. G., Molokeev M. S., Krylov A. S., Bazarov B. G., Bazarova J. G., Lin Z. S.
Заглавие : Electronic structure of β-RbSm(MoO4)2 and chemical bonding in molybdates
Коллективы : Ministry of Education and Science of the Russian Federation; National Natural Science Foundation of China [11174297, 11474292]; National Basic Research Project of China [2011CB922204]; Foundation of the Director of Technical Institute of Physics and Chemistry, CAS; RAS [24-29]; RFBR [13-02-00825]
Разночтения заглавия :. в WoS: Electronic structure of beta-RbSm(MoO4)2 and chemical bonding in molybdates
Место публикации : Dalton Trans.: Royal Society of Chemistry, 2015. - Vol. 44, Is. 4. - P.1805-1815. - ISSN 1477-9226, DOI 10.1039/c4dt03203a. - ISSN 1477-9234
Примечания : Cited References: 121. - VVA and ASA gratefully acknowledge the Ministry of Education and Science of the Russian Federation for financial support. ZL acknowledges the support by National Natural Science Foundation of China (11174297 and 11474292), the National Basic Research Project of China (2011CB922204), and Foundation of the Director of Technical Institute of Physics and Chemistry, CAS. The work was partially supported by RAS Project 24-29 and RFBR Grant 13-02-00825.
Предметные рубрики: RAY PHOTOELECTRON-SPECTROSCOPY
CRYSTAL-STRUCTURE
X-RAY
NEUTRON-DIFFRACTION
MAGNETIC-PROPERTIES
PHASE-FORMATION
CORE LEVELS
2ND-HARMONIC GENERATION
LUMINESCENCE PROPERTIES
VIBRATIONAL PROPERTIES
Аннотация: Microcrystals of orthorhombic rubidium samarium molybdate, beta-RbSm(MoO4)(2), have been fabricated by solid state synthesis at T = 450 degrees C, 70 h, and at T = 600 degrees C, 150 h. The crystal structure has been refined by the Rietveld method in space group Pbcn with cell parameters a = 5.0984(2), b = 18.9742(6) and c = 8.0449(3) angstrom (R-B = 1.72%). Thermal properties of beta-RbSm(MoO4)(2) were traced by DSC over the temperature range of T = 20-965 degrees C, and the earlier reported β ↔ α phase transition at T similar to 860-910 degrees C was not verified. The electronic structure of beta-RbSm(MoO4) 2 was studied by employing theoretical calculations and X-ray photoelectron spectroscopy. It has been established that the O 2p-like states contribute mainly to the upper part of the valence band and occupy the valence band maximum, whereas the Mo 4d-like states contribute mainly to the lower part of the valence band. Chemical bonding effects have been analysed from the element core level binding energy data. In addition, it was found that the luminescence spectrum of beta-RbSm(MoO4)(2) is rather peculiar among the Sm3+ containing materials. The optical refractive index dispersion in beta-RbSm(MoO4)(2) was also predicted by the first-principles calculations.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S., Udod L. V., Sitnikov M. N., Shestakov N. P.
Заглавие : Bi2(Sn0.95Cr0.05)2O7: Structure, IR spectra, and dielectric properties
Место публикации : Ceram. Int.: Elsevier, 2016. - Vol. 42, Is. 4. - P.5177-5183. - ISSN 02728842 (ISSN), DOI 10.1016/j.ceramint.2015.12.040
Примечания : Cited References: 45. - This work was supported by the Russian Foundation for Basic Research Projects no. 15-42-04099 r_siberia_a, Siberian Branch of Science and NAS of Belarus “Electronic and magnetic phase transitions in materials with magnetoelectric affect” and government work no. 114090470016.
Предметные рубрики: BISMUTH PYROSTANNATE
PYROCHLORE STRUCTURE
MAGNETIC-PROPERTIES
PARTIAL OXIDATION
HIGH-TEMPERATURE
X-RAY
Bi2Sn2O7
SUBSTITUTION
CATALYSTS
DIFFRACTION
Ключевые слова (''Своб.индексиров.''): bismuth pyrostannate--infrared absorption spectra--structural transition--permittivity--debye model
Аннотация: Infrared absorption spectra of the bismuth pyrostannate Bi2(Sn0.95Cr0.05)2O7 were investigated in the frequency range 350-1100 cm-1 at temperatures of 110-525 K. Four frequency regions with split absorption lines are distinguished. Softening of frequencies at the structural transitions was observed. The maxima of permittivity measured in the frequency range 1-200 kHz at temperatures 100-400 K were determined. It was found that the magnetic susceptibility changes its sign in the low-temperature region. The correlation between anomalies in the magnetic susceptibility, permittivity, and absorption line intensity was established. Softening of frequencies is explained by the variation in the coefficient of thermal expansion of the lattice. The temperature behavior of permittivity is described using the Debye model. © 2015 Elsevier Ltd and Techna Group S.r.l.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pogorel'tsev E. I., Mel'nikova S. V., Kartashev A. V., Gorev M. V., Flerov I. N., Laptash N. M.
Заглавие : Thermal, optical, and dielectric properties of Fluoride Rb2TaF7
Коллективы : Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund [16-42-243001]
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2017. - Vol. 59, Is. 5. - P.986-991. - ISSN 1063-7834, DOI 10.1134/S1063783417050250. - ISSN 1090-6460(eISSN)
Примечания : Cited References:21. - The reported study was funded by the Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund to the research project no. 16-42-243001.
Предметные рубрики: PHASE-TRANSITIONS
X-RAY
DISORDER
NMR
DIFFRACTION
OXYFLUORIDE
Аннотация: The thermal, optical, and dielectric properties of fluoride Rb2TaF7 were investigated. It was observed that the variation in chemical pressure in fluorides A2+TaF7 caused by the cation substitution of rubidium for ammonium does not affect the ferroelastic nature of structural distortions, but leads to stabilization of the high- and low-temperature phases and enhancement of birefringence. The entropy of the phase transition P4/nmm ↔ Cmma is typical of the shift transformations, which is consistent with a model of the initial and distorted phase structures. The anisotropy of chemical pressure causes the change of signs of the anomalous strain and baric coefficient dT/dp of Rb2TaF7 as compared with the values for its ammonium analog.
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