共查询到20条相似文献,搜索用时 31 毫秒
1.
I. P. Aleksandrova A. A. Sukhovsky Yu. N. Ivanov I. P. Raevsky 《Physics of the Solid State》2012,54(2):316-323
The local structure of the ferroelectric-relaxor PbSc1/2Nb1/2O3 in the temperature range from 550 to 220 K has been investigated using 45Sc nuclear magnetic resonance. It has been found that, in the paraelectric phase at temperatures below 550 K, the crystal
consists of regions of an ordered elpasolite structure and inclusions of the disordered tetragonal perovskite phase with displacements
along directions of the [001] type. The relative weight of the tetragonal structure in the region of the paraelectric phase
is approximately equal to 0.28. Below the temperature of the phase transition from the disordered modification to the polar
phase, the relative weight of the tetragonal phase decreases with decreasing temperature. The tetragonal structure is replaced
by the trigonal polar structure. In a wide temperature range (∼50 K), there exists a heterophase structure that is characteristic
of relaxors. Note that the correlation length of displacements in the tetragonal phase should be very small to explain the
absence of indications of the existence of this phase in the diffraction data. 相似文献
2.
A. V. Pavlenko A. V. Turik L. A. Shilkina S. P. Kubrin Yu. V. Rusalev L. A. Reznichenko I. N. Andryushina 《Physics of the Solid State》2018,60(3):515-519
Polycrystalline samples of SrFe2/3W1/3O3 (SFWO) ceramic were obtained by solid-phase reactions with subsequent sintering using conventional ceramic technology. X-ray diffraction analysis showed that at room temperature, the SFWO ceramic is single-phase and has a perovskite-type structure with tetragonal symmetry and parameters a = 3.941(9) Å, c = 3.955(6) Å, and c/a = 1.0035. In studying the magnetic properties and the Mössbauer effect in SFWO ceramics, it is found that the material is a ferrimagnet, and the iron ions are only in the valence state of Fe3+. It is suggested that in the temperature range of T = 150–210°C, a smeared phase transition from a cubic (paraelectric) phase to a tetragonal (ferroelectric) phase takes place in SFWO with decreasing temperature. 相似文献
3.
G. A. Politova I. S. Tereshina G. S. Burkhanov O. D. Chistyakov V. B. Chzhan V. I. Nizhankovskii A. Zaleski T. P. Kaminskaya V. V. Popov 《Physics of the Solid State》2011,53(10):2028-2031
A complex investigation of the structural, magnetic, and magnetothermal properties of the Tb0.3Dy0.7Co2 compound synthesized with the use of high-purity rare-earth metals has been performed. The phase composition has been controlled
using the X-ray structural analysis, and the topology of the alloy surface has been investigated using atomic-force microscopy.
It has been established that the Tb0.3Dy0.7Co2 compound is single-phase, while the samples selected for measurements possess a clearly pronounced texture. The magnetization
has been measured using a vibrating-sample magnetometer in the fields up to 100 kOe in a temperature range from 4.2 to 200
K. The Curie temperature of the compound is 170 K. The data on the temperature dependence of heat capacity of Tb0.3Dy0.7Co2 have been obtained. The magnetocaloric effect ΔT has been measured by a direct method in the fields up to 18 kOe applied both along and perpendicularly to the texture axis.
The anisotropic behavior of the magnitude ΔT for this compound, which possesses the cubic structure, has been found. The maximum value of the magnetocaloric effect ΔT = 2.3 K (ΔH = 18 kOe) has been observed upon applying the magnetic field along the texture axis. 相似文献
4.
V. I. Zinenko N. G. Zamkova S. N. Sofronova 《Journal of Experimental and Theoretical Physics》2003,96(4):747-756
The results of nonempirical calculation of energies of three polytypes (cubic, two-layer hexagonal, and six-layer hexagonal) are given for RbMnX3 (X = F, Cl, Br) crystals. The calculation is performed using an ionic crystal model with regard for the deformability and the dipole and quadrupole polarizabilities of ions. The behavior of these crystals under the action of hydrostatic pressure is studied. It is demonstrated that, at normal pressure, the RbMnCl3 and RbMnBr3 crystals have a six-layer hexagonal structure. At pressures above 11 kbar, RbMnCl3 passes to a phase with a cubic structure; RbMnBr3 at pressures above 90 kbar passes to a phase with a two-layer hexagonal structure. The RbMnF3 crystal under normal conditions has a cubic structure and experiences no phase transformations under the effect of pressure. The obtained results are in satisfactory agreement with the known experimental data. 相似文献
5.
Vladimir A. Kulbachinskii Boris M. Bulychev Vladimir G. Kytin Alexey V. Krechetov Valeriy P. Tarasov Elizaveta A. Konstantinova Yuriy A. Velikodnyi Yuriy B. Muravlev Andrey V. Zoteev 《Central European Journal of Physics》2010,8(1):101-112
Sodium fullerides Na
n
C60 (n = 2, 3) have been synthesized by a liquid phase reaction and investigated with X-ray diffraction (XRD), nuclear magnetic
resonance (NMR), electron paramagnetic resonance, and differential thermal analysis. XRD data indicate that the crystal structure
of Na2C60 at 300 K is face centered cubic (FCC). A phase transition from primitive cubic to FCC crystal structure has been observed
in this work in Na2C60 fulleride at 290 K. The transition is accompanied by the step-like change of paramagnetic susceptibility. The crystal structure
of Na3C60 is more complicated than, and different from, what has been reported in the literature. A nearly seven-fold increase of paramagnetic
susceptibility with increasing temperature has been observed in the Na3C60 fulleride at 240–260 K. In the same temperature range, a new line at about 255 ppm appears in the 23Na NMR spectrum, indicating a significant increase of electron density near the Na nucleus. The observed effect can be explained
by a metal-insulator transition caused by a structural transition. 相似文献
6.
V. I. Maksimov T. P. Surkova V. D. Parkhomenko E. N. Yushkova 《Physics of the Solid State》2016,58(4):650-659
The structural state of a bulk Zn0.95Fe0.05Se cubic crystal grown by the chemical transport method from the gas phase has been investigated using thermal neutron diffraction at room temperature. It has been found that the measured neutron diffraction patterns of the crystal, in addition to structural Bragg peaks, contain a clearly identified system of superstructure reflections with the wave vector k = (1/3 1/3 1/3)2π/a (where a is the parameter of the cubic unit cell), which is interpreted as a clear evidence of the incipient transition state preceding the concentration phase transformation fcc ? hcp. It has been shown that the resulting structural state includes an inhomogeneous microstrain field with the possible appearance of long-wavelength modulations based on the initial sphalerite structure. 相似文献
7.
S. F. Dubinin V. I. Maksimov V. D. Parkhomenko V. I. Sokolov A. N. Baranov P. S. Sokolov Yu. A. Dorofeev 《Physics of the Solid State》2011,53(7):1362-1366
The fine structure and spin system of the cubic oxide Ni0.3Zn0.7O compound prepared from the initial hexagonal phase by quenching a sample with a high temperature and applying an external
hydrostatic pressure to it have been studied using magnetic measurements, synchrotron and X-ray diffraction. It has been revealed
that the diffraction patterns of this compound contain a system of weak diffuse maxima with the wave vectors q = (1/6 1/6 1/6)2π/a and (1/3 1/3 1/3)2π/a, along with strong Bragg peaks of the cubic phase. It has been shown that the origin of the diffuse peaks is due to longitudinal
and transverse displacements of ions with respect to symmetric crystallographic directions of the {111} type. The reasons
for the ion displacement and specific features of the structure of the spin system of the strongly correlated oxide Ni0.3Zn0.7O compound have been briefly discussed. 相似文献
8.
9.
E. I. Pogorel’tsev E. V. Bogdanov M. S. Molokeev V. N. Voronov L. I. Isaenko S. A. Zhurkov N. M. Laptash M. V. Gorev I. N. Flerov 《Physics of the Solid State》2011,53(6):1202-1211
According to the results of calorimetric and structural studies, the Fm{ie1202-1}m phase in K2NaMoO3F3 remains stable at least to 100 K. No ferroelectric transformation assumed earlier has been revealed in a series of Rb2KMoO3F3 samples prepared using various technologies. Only a phase transition of nonferroelectric origin has been observed near 195
K, and its thermodynamic characteristics have been determined. An analysis of the stability of the cubic structure of molybdenum
fluorine-oxygen elpasolites-cryolites has been performed in the framework of the hypothesis on strengths of interatomic bonds.
The barocaloric effect in Rb2KMoO3F3 has been estimated. 相似文献
10.
The absorption spectrum of Cs2ZnI4 thin films in the energy range 3–6 eV at temperatures from 90 to 340 K has been investigated. It is established that this compound belongs to direct-gap insulators. Low-frequency exciton excitations are localized in ZnI4 structural elements of the lattice. Phase transitions at 280 K (paraelectric phase ? incommensurate phase), 135 K (incommensurate phase ? monoclinic ferroelastic phase), and 96 K (monoclinic phase ? triclinic ferroelastic phase) have been found from the temperature dependences of the spectral position and halfwidth of the low-frequency exciton band. Additional broadening of the exciton band is observed for ferroelastic phases; it is likely to be due to exciton scattering from strain fluctuations near domain walls. 相似文献
11.
S. G. Jabarov D. P. Kozlenko S. E. Kichanov A. V. Belushkin B. N. Savenko R. Z. Mextieva C. Lathe 《Physics of the Solid State》2011,53(11):2300-2304
The crystal structure of lead titanate PbTiO3 was investigated by energy dispersive X-ray diffraction at high pressures up to 4 GPa in a temperature range of 300–950 K.
At the ambient conditions, the PbTiO3 structure is tetragonal with the space group P4mm (ferroelectric phase). A structural phase transition into the cubic phase with a space group Pm[`3]mPm\bar 3m is observed at T = 747 K. It was found that the phase transition temperature decreases upon applying the high pressure with the coefficient
dT
C
/dP = -65 K/GPa. Dependences of parameters and volume of the unit cell on the pressure and temperature was found, and the bulk
modulus and thermal expansion coefficients for the tetragonal and cubic phases of lead titanate have been calculated. 相似文献
12.
V. P. Kolko R. I. Gulyaev E. M. Moroz A. I. Boronin G. R. Kosmambetova A. V. Guralsky P. Y. Strizhak 《Bulletin of the Russian Academy of Sciences: Physics》2008,72(8):1098-1102
Cu-CeO2 catalysts deposited on a commercial ZrO2 support have been investigated. The catalyst composition has been optimized: the optimum copper content was found to be 5–10 wt % at a cerium oxide content of 23 wt %. The catalysts were investigated by X-ray diffraction analysis and X-ray photoelectron spectroscopy. According to the X-ray diffraction data, the support consists of the monoclinic ZrO2 phase and cubic CeO2 phase with an enlarged lattice parameter, while the catalysts contain CuO. The X-ray photoelectron data indicate the presence of a highly dispersed CuO2 phase interacting with cerium oxide and zirconia on the surface of the catalyst having the optimum copper content. 相似文献
13.
V. D. Fokina E. V. Bogdanov M. V. Gorev M. S. Molokeev E. I. Pogorel’tsev I. N. Flerov N. M. Laptash 《Physics of the Solid State》2010,52(4):781-788
The thermal and dielectric properties of the (NH4)2NbOF5 oxyfluoride have been investigated. It has been established that the structural phase transitions Cmc21 → 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. 相似文献
14.
B. Yu. Sokolov 《Physics of the Solid State》2011,53(8):1581-1587
The transformation of a domain structure and technical magnetization of the Tb0.2Y2.8Fe5O12 single crystal in the temperature range of the spontaneous orientational phase transition have been investigated by the magneto-optical
method. It has been shown that the phase transition is extended in a certain temperature range in which domains of the low-temperature
and high-temperature magnetic phases coexist. It has been found that the evolution of the domain configuration in the temperature
range of spin reorientation substantially depends on the presence of mechanical stresses in the crystal. Anomalies in the
temperature dependences of the coercivity and magneto-optical susceptibility of the crystal due to the transformation of its
domain structure during the phase transition have been revealed. The experimental results have been interpreted within the
existing theory of orientational phase transitions in cubic crystals. 相似文献
15.
G. E. Abrosimova A. S. Aronin N. S. Afonikova N. P. Kobelev 《Physics of the Solid State》2010,52(9):1892-1898
The influence of plastic deformation on the structure of the Pd40Ni40P20 amorphous alloy has been investigated using X-ray diffraction and measurements of the velocity of sound. It has been revealed
that the rolling of the sample leads to a change in the structure of the amorphous phase (distortion of the first coordination
sphere) and that the structural transformations are more pronounced in the near-surface region of the sample. The rolling
also results in a decrease in the transverse velocity of sound. The observed effects decrease with time. It has been demonstrated
that the revealed effects are associated with the inelastic deformation of the amorphous alloy. 相似文献
16.
The structures of two phases of the (NH4)3Nb(O2)2F4 crystal, namely, the parent cubic phase and the most distorted low-temperature phase, have been determined from data of an
X-ray diffraction experiment performed for a powder sample. The profile and structural parameters have been refined according
to the procedure implemented in the DDM program. The results obtained have been discussed with invoking the group-theoretical
analysis of the complete order parameter condensate, which takes into account the critical and noncritical atomic displacements
and allows the interpretation of the obtained experimental data. It has been found that the most probable sequence of structural
transformations occurring in the crystal can be schematically represented in the following form:
_boxclose_boxclose_boxclose_boxclose_boxclose_boxclose_boxclose_boxclose] _5^ + (11 - 7)C2/mP2_1 /m | #xA; P2_1 /n. | #xA; |
#xA;\begin{gathered}
Fm\bar 3m\xrightarrow[{(\eta 1,\eta 1,\eta )}]{{\Gamma _5^ + (11 - 7)}}C2/m\xrightarrow[{(\eta 1,\eta 1,\eta )(0,0,0,0,0,\xi ,0 - \xi ,0,0,0,0)}]{{\Gamma _5^ + (11 - 7) \otimes \Sigma _2 (4 - 2)}}P2_1 /m \hfill \\
\xrightarrow[{(\eta 1,\eta 1,\eta )(0,0,0,0,0,\xi ,0 - \xi ,0,0,0,0)(0,0,0,0,0,\varepsilon ,0,\varepsilon ,0,0,0,0)}]{{\Gamma _5^ + (11 - 7) \otimes \Sigma _2 (4 - 2) \otimes \Sigma _3 (4 - 3)}}P2_1 /n. \hfill \\
\end{gathered}
相似文献
17.
The atom-vacancy ordering of cubic vanadium monoxide VO1.29, which has basis cubic structure B1 and structural vacancies in the metal sublattice, has been studied using the x-ray diffraction method. It has been shown that the formation of the tetragonal (space group I41/amd) ordered phase V52O64 of cubic vanadium monoxide VOy proceeds as a first-order phase transition through the disorder-order channel including 22 nonequivalent superstructure vectors of four stars {k 10}, {k 4}, {k 3}, and {k 2}. The distribution function of the vanadium atoms in the V52O64 tetragonal superstructure has been calculated. 相似文献
18.
Yu. G. Chukalkin A. E. Teplykh A. N. Pirogov D. G. Kellerman 《Physics of the Solid State》2010,52(12):2545-2551
The specific features of the crystal structure and the magnetic state of stoichiometric lithium manganite in the structurally
ordered Li[Mn2]O4 and disordered Li1 − δMnδ[Mn2 − δLiδ]O4 (δ = 1/6) states have been investigated using neutron diffraction, X-ray diffraction, and magnetic methods. The structurally
disordered state of the manganite was achieved under irradiation by fast neutrons (E
eff ≥ 1 MeV) with a fluence of 2 × 1020 cm−2 at a temperature of 340 K. It has been demonstrated that, in the initial sample, the charge ordering of manganese ions of
different valences arises at room temperature, which is accompanied by orthorhombic distortions of the cubic spinel structure,
and the long-range antiferromagnetic order with the wave vector k = 2π/c(0, 0, 0.44) is observed at low temperatures. It has been established that the structural disordering leads to radical changes
in the structural and magnetic states of the LiMn2O4 manganite. The charge ordering is destroyed, and the structure retains the cubic symmetry even at a temperature of 5 K. The
antiferromagnetic type of ordering transforms into ferrimagnetic ordering with local spin deviations in the octahedral sublattice
due to the appearance of intersublattice exchange interactions. 相似文献
19.
A. I. Lebedev 《Physics of the Solid State》2011,53(12):2463-2467
First-principles density functional theory is used to calculate the phonon spectrum in the paraelectric phase, the ground-state
structure and polarization distribution in the polar phase, and energies of ferro- and antiferroelectrically ordered phases
of free-standing (KNbO3)1(KTaO3)
n
ferroelectric superlattices with n = 1–7. It is established that quasi-two-dimensional ferroelectricity with polarization oriented in the layer plane, which
weakly interacts with polarization in neighboring layers, appears in potassium niobate layers with a thickness of one unit
cell in the superlattices. The possibility of using of such ferroelectric superlattices as a medium for three-dimensional
information recording is shown. 相似文献
20.
Single crystal of a new organic–inorganic hybrid material [C6H10(NH3)2]3CuBr4.3Br was synthesized by the slow evaporation method at room temperature and characterized by X-ray diffraction, FTIR, Raman spectroscopy, UV–Vis, dielectric measurements, and Hirschfield surface analysis. The title compound crystallizes in trigonal system \( P\overline{3} \).The crystal packing is governed by the N-H…Br and non-classical C-H…Br hydrogen-bonding interactions between the 1, 2-diamoniumcyclohexane cations, the tetrahedral [CuBr4]3? anions, and the isolated ion Br?. Theoretical calculations were performed using density functional theory (DFT) for studying the molecular structure, vibrational spectra, and optical properties of the investigated molecule in the ground state. The optimized geometrical parameters obtained by DFT calculations are in good agreement with single crystal XRD data. The optical properties were investigated by optical absorption and show two bands at 260 and 305 nm. 相似文献
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