共查询到20条相似文献,搜索用时 31 毫秒
1.
S. V. Popova O. A. Sazanova V. V. Brazhkin N. V. Kalyaeva M. B. Kondrin A. G. Lyapin 《Physics of the Solid State》2006,48(11):2177-2182
The effect of high pressure (6 GPa) on the formation of new phases in a polycrystalline mixture GaSb: Mn = 1: 1 upon heating was studied. Sphalerite-type solid solutions with a small amount of Mn form at temperatures below 520–600 K. At higher temperatures, new crystalline GaSbMn phases are synthesized: a phase with a simple cubic structure with a lattice parameter a = 2.946 ± 0.001 Å (at 620–670 K) and a phase with a tetragonal CuAl2-type structure (space group I4/mcm) with lattice parameters a = 6.426 ± 0.004 Å and c = 5.349 ± 0.004 Å (at 690–870 K). These new phases are metastable under normal conditions and have magnetic properties. The structure, conductivity, and thermal stability of the synthesized phases are investigated, and the products of decomposition of these new phases upon annealing are analyzed. 相似文献
2.
X-ray diffraction studies are reported on silicon at pressures up to 250 kbar (25 GPa). A transition to the β-Sn structure (II) initiates at 112 ± 2 kbar and two phases (I + II) coexist to 125 ± 2 kbar. At 132 ± 2 kbar a new phase (V) initiates, and the transition is complete at 164 ± 5 kbar. This phase persists to 250 kbar. Its structure is tentatively assigned as primitive hexagonal with c/a = 0.941 ± 0.002 at 250 kbar. On release of pressure, the sequence is V → (V + II) (145 - 110 kbar) → II → (II + III) (108 - 85 kbar) → III, the last phase persisting to room pressure. 相似文献
3.
Electron paramagnetic resonance measurements in single crystals of NiSiF6. 6D2O were made at K, Ku and Ka bands at 4.2 K and between 77 K and 300 K. The measured g values were in the range 2.23–2.26, while the zero-field splitting parameter D varied from ?(0.185 ± 0.005) cm?1 at 4.2 K to ?(0.53 ± 0.01) cm?1 at 298 K. The parameters of the trimolecular hexagonal unit cell were determined to be approximately a = 9.28 Å, c = 9.58 Å from powder X-ray diffraction measurements at room temperature. 相似文献
4.
A new polymorph of GaAsO 4 has been synthesised at high pressure and temperature (60 kbar and 1273 K). Samples were characterised by powder X-ray diffraction, scanning electron microscopy and EDAX spectroscopy. This material shows an hexagonal symmetry with cell parameters, a =8.1931(4) Å and c =4.3744(2) Å; particles are of hexagonal shape with a narrow size distribution around 2-3 w m and composition close to the Ga:As atomic ratio=1:1. This new high pressure phase of GaAsO 4 represents a new transition path for the ABO 4 compounds. 相似文献
5.
U. Shmueli V. Steinberg T. Sverbilova A. Voronel 《Journal of Physics and Chemistry of Solids》1981,42(1):19-22
Solid equiatomic K-Cs alloys have been investigated by X-ray diffraction throughout the temperature range 300-100K. The results indicate that a phase separation occurs below 185K accompanied by the appearance of an ordered phase in this range. This phase has a hexagonal lattice with parameters: a = 9.32(1) Å and c = 11.80(2) Å (at 170K). Evidence from our other studies [7] indicates that its composition is K2Cs. Another phase transformation in this ordered crystal is observed below 120K. There is no change of lattice symmetry but the unit cell constants shrink to the values: a = 9.11(1) Å and c = 10.86(2) Å (at 100K). The transformation can be ascribed to a rearrangement of the electronic structure of Cs. 相似文献
6.
I. O. Bashkin A. Yu. Pagnuev A. F. Gurov V. K. Fedotov G. E. Abrosimova E. G. Ponyatovskii 《Physics of the Solid State》2000,42(1):170-176
The effect of pressure on the α ? β and ω ? β transformations in the equiatomic alloy TiZr is studied by the differential thermal analysis (DTA) and calorimetric technique. The α-β equilibrium at atmospheric pressure occurs at a temperature of 579°C, and the heat of transition ΔH is 40.9±2.0 J/g. As the pressure increases up to 28 kbar, the temperature of the α-β equilibrium linearly decreases, dT/dP=?2.2±0.3 K/kbar. In the pressure range 28–48 kbar, the β-phase undergoes a transition to the two-phase (α + ω) state upon cooling to room temperature. At pressures above the triple point with the coordinates P=49±3 kbar and T=460±30°C, the cooling of the β-phase gives rise to only the hexagonal ω-phase with the unit cell parameters a=4.843 Å, c=2.988 Å, and c/a=0.617 under normal conditions. The slope of the ω-β equilibrium boundary is positive at pressures up to 70 kbar, dT/dP≈0.46 K/kbar. The ω → α transformation at atmospheric pressure proceeds in the temperature range T=425–470°C with the enthalpy of transition ΔH=2.8 J/g. 相似文献
7.
Lin-gun Liu 《Journal of Physics and Chemistry of Solids》1975,36(1):31-35
The effect of pressure on the lattice parameters of the h.c.p. phase of Lu has been studied up to 230 kbar at 23 ± 3°C by means of X-ray diffraction employing a diamond-anvil cell. The data fitted to the Birch equation yield an isothermal bulk modulus of 460 ± 20 kbar with a pressure derivative of 2.8 ± 0.5. The axial ratio decreases nonlinearly with increasing pressure, the decrease being 2.4 per cent at 230 kbar. When the pressure exceeds 230 kbar, Lu transforms reversibly from the h.c.p. phase to the Sm-type structure. The transition occurs with increasing pressure in the range of 230 ± 5 kbar. The lattice parameters of the Sm-type structure at about 231 kbar are a = 3.176 ± 0.006 Å and c = 21.77 ± 0.04 Å, and the volume change is or ?1.6 per cent of the volume of the h.c.p. phase. 相似文献
8.
Crystalline hexagonal B(N 1 m x C x ) and cubic B-C-N compounds have been synthesized from a precursor produced from melamine and boric acid by application of high temperature and high pressure. The synthesized products were characterized by X-ray diffraction. The lattice parameters for the hexagonal crystal are a=2.506 Å, c=6.657 Å, and that for the cubic crystal is a=3.596 Å. The X-ray photoelectron spectra of the B-C-N compound indicate the presence of B-N, C-N, C-C, and B-C bonds, which suggests that boron, carbon, and nitrogen atoms all bond with one another and that the B-C-N crystal is a compound in which the three kinds of atoms are mixed atomically. The composition of the B-C-N compound is B 0.47 C 0.23 N 0.30 . A strong absorption band at 1000~1120 cm m 1 attributable to the cubic B-C-N phase is observed in the infrared spectrum. The photoluminescence spectrum of hexagonal B-C-N powder measured at room temperature features a broad peak centered at 374 nm, corresponding to the band-edge emission of h-B-C-N, and is similar to that of w-GaN. 相似文献
9.
BaBi0.7Nb0.3O3, an ordered perovskite, crystallizes in a centrosymmetric rhombohedral structure with the space group R3¯. The refined cell parameters obtained from synchrotron powder X-ray diffraction data for the rhombohedral phase at ambient pressure are a=6.109 (2) Å and α=60.3 (1)°. The pressure-dependent synchrotron powder X-ray diffraction studies show a phase transition around 8.44±1 GPa, where it transforms from rhombohedral structure to a monoclinic structure. The lattice parameters obtained for the monoclinic phase at a pressure of 15±1 GPa are a=5.91 (2) Å, b=6.25 (3) Å and c=8.22 (1) Å with monoclinic angle, β=88 (1)°. 相似文献
10.
N. B. Bolotina V. V. Brazhkin T. I. Dyuzheva Y. Katayama L. F. Kulikova L. V. Lityagina N. A. Nikolaev 《JETP Letters》2014,98(9):539-543
At normal pressure, the As2S3 compound is the most stable equilibrium modification with unique layered structure. The possibility of high-pressure polymorphism of this substance remains questionable. Our research showed that the As2S3 substance was metastable under pressures P > 6 GPa decomposing into two high-pressure phases: As2S3 → AsS2 + AsS. New AsS2 phase can be conserved in the single crystalline form in metastable state at room pressure up to its melting temperature (470 K). This modification has the layered structure with P1211 monoclinic symmetry group; the unit-cell values are a = 7.916(2) Å, b = 9.937(2) Å, c = 7.118(1) Å, β = 106.41° (Z = 8, density 3.44 g/cm3). Along with the recently studied AsS high-pressure modification, the new AsS2 phase suggests that high pressure polymorphism is a very powerful tool to create new layered-structure phases with “wrong” stoichiometry. 相似文献
11.
A. M. Tikhonov 《JETP Letters》2015,102(8):552-556
A sharp phase transition from a crystalline state with the area per molecule A = (17 ± 1) Å2 to a liquid state with A = (23 ± 1) Å2 at the n-hexane–water interface in a Gibbs monolayer of melissic acid has been revealed in data of X-ray reflectometry with the use of synchrotron radiation. 相似文献
12.
G. N. Stepanov 《Physics of the Solid State》2014,56(8):1561-1568
The dependence of the unit cell volume of BaSnO3 on the pressure up to 15 GPa has been investigated and the constants of the Murnaghan equation of state B 0 = 178.39 ± 4.09 GPa and B′0 = 4.68 ± 0.56 have been obtained using the X-ray diffraction method. The change of the isomer shift (IS) in BaSnO3 with a variation in the pressure P has been examined using the gamma resonance method. This quantity is ?IS(P)/?P = ?(0.00474 ± 0.0002) mm s?1 GPa?1 or, taking into account the measurements of the unit cell parameter under pressure, ?IS/?L = 1.42 mm s?1Å?1, where L is the tin-oxygen distance. 相似文献
13.
A small polycrystalline ingot sample of NpCo2Si2 (weight ≈ 1.5 g) has been studied by neutron diffration between 2 and 160 K on the multi-detector D1B of ILL, Grenoble. At 100 K, the crystal structure is body-centered tetragonal (space group 14/mmm) with a = 3.886 Å and c =9.649 Å. Below TN = (44 ± 2) K, seven superlattice lines are observed which correspond to a simple tetragonal lattice with lattice constants as above. They are consistent with a type I antiferromagnetic structure of the Np (2a) sublattice, with (001) ferromagnetic sheets coupled antiferromagnetically according to the sequence +-+-. At 6 K, the neptunium moment obtained from the diffracted intensities is: (1.48 ± 0.20)μuB, and makes an angle 52° ± 15° with the c axis. The cobalt moment is certainly smallet than 0.3μuB. The Np moment correlates well with the 237Np hyperfine field deduced from Mos?sbauer spectroscopy; the sublattice magnetization-temoperature curve follows very well the brillouin curve. The magnetism is therefore probably of lovalized character in this compound. An isomorphous sample of NpCu2Si2 (a = 3.990 Å c = 9.920 Å) was shown to be ferromagnetic below (41 ± 2) K, with the Np moment [1.5 ± 0.2)μuB] aligned along the c axis. 相似文献
14.
B. Lengeler 《Solid State Communications》1985,55(8):679-682
The local lattice structure around B atoms in Pd was determined from the EXAFS at the K-edge of' Pd in to alloys with B/Pd = 16 and 11.4 %. It was confirmed that B occupies octahedral interstices in the fcc lattice of Pd. The lattice expansion of the Pd matrix by the dissolved B is da/a = (0.169±0.003) for B/Pd = 1. Boron displaces its 6 nearest Pd neighbors outwards by (0.106 ± 0.005)Å relative to pure Pd and by (0.061 ± 0.005)Å relative to the average lattice. The local lattice distortion has practically vanished beyond the second Pd neighbors. 相似文献
15.
Z. A. Samoilenko E. I. Pushenko N. N. Ivakhnenko B. E. Shkuratov V. N. Varyukhin 《Technical Physics》2007,52(5):631-635
The structure of amorphous CNx-TiN films grown by ion-stimulated deposition at a bias voltage U = 200–500 V is studied by X-ray diffraction. As the bias voltage increases in the range U = 300–360 V, the CNx-TiN films are shown to undergo a phase transition in the amorphous phase having different order scales (20–50 Å): this transition is related to an increase in the content of the fraction of medium-cell (4 Å) carbon clusters as compared to the fractions of clusters with large (8 Å) and small (2 Å) cells. Under these conditions, 80–150 Å crystalline clusters undergo the phase transition from the Ti2C(N) carbide into graphite (C g) and diamond (Cd); the last two phases are represented by 100-Å clusters. 相似文献
16.
A detailed LEED study is reported of the surface phases stabilised by hydrogen chemisorption on W {001}, over the temperature range 170 to 400 K, correlated with absolute determinations of surface coverages and sticking probabilities. The saturation coverage at 300 K is 19(± 3) × 1014 atoms cm?2, corresponding to a surface stoichiometry of WH2, and the initial sticking probability for both H2 and D2 is 0.60 ± 0.03, independent of substrate temperature down to 170 K. Over the range 170 to 300 K six coverage-dependent temperature-independent phases are identified, and the transition coverages determined. As with the clean surface displacive phase, the c(2 × 2)-H phase is inhibited by the presence of steps and impurities over large distances (~20 Å), again strongly indicative of CDW-PLD mechanisms for the formation of the H-stabilised phases. These phases are significantly more temperature stable than the clean , the most stable being a c(2 × 2)-H split half-order phase which is formed at domain stoichiometries between WH0.3 and WH0.5. LEED symmetry analysis, the dependence of half-order intensity and half-width on coverage, and I-V spectra indicate that the c(2 × 2)-H phase is a different displacive structure from that determined by Debe and King for the clean . LEED I-V spectra are consistent with an expansion of the surface-bulk interlayer spacing from 1.48 to 1.51 Å as the hydrogen coverage increases to ~4 × 1014 atoms cm?2. The transition from the split half-order to a streaked half-order phase is found to be correlated with changes in a range of other physical properties previously reported for this system. As the surface stoichiometry increases from WH to WH2 a gradual transition occurs between a phase devoid of long-range order to well-ordered (1 × 1)-H. Displacive structures are proposed for the various phases formed, based on the hypothesis that at any coverage the most stable phase is determined by the gain in stability produced by a combination of chemical bonding to form a local surface complex and electron-phonon coupling to produce a periodic lattice distortion. The sequence of commensurate, incommensurate and disordered structures are consistent with the wealth of data now available for this system. Finally, a simple structural model is suggested for the peak-splitting observed in desorption spectra. 相似文献
17.
Marlin D. Harmony S.N. Mathur Stuart J. Merdian 《Journal of Molecular Spectroscopy》1979,75(1):144-149
The microwave spectrum of methylene chloride has been reinvestigated in order to obtain a complete substitution (rs) structure of well-defined precision. Measurements on the 13CH2Cl2 species have yielded the following rigid-rotor rotational constants: A = 30746.20 ± 0.10 MHz, B = 3320.63 ± 0.11 MHz, and C = 3053.44 ± 0.10 MHz. These data, combined with revised values reported earlier for other isotopic species, yields the following rs structural parameters: CCl = 1.767 ± 0.002 Å, CH = 1.085 ± 0.002 Å, ∠HCH = 112.1 ± 0.2°, and ∠ClCCl = 112.2 ± 0.1°. 相似文献
18.
N D Kataria Mukesh Kumar V S Tomar V N Ojha G S N Reddy K C Nagpal A K Gupta 《Pramana》1989,32(1):83-88
Starting composition 1112 for Bi-Sr-Ca-Cu-oxide yields multiphase super-conductors with the proportion of constituent phases depending sensitively on the annealing temperature. The R-T curves show zero resistivity and the transition corresponding toT c = 80 K phase prominently. However, indexing of X-ray diffraction peaks reveals presence of 80 K (lowT c) as well as 108 K (highT c) phase. The lowT c phase thus corresponds to the orthorhombic structure with a unit cell ofa = 5.4Å,b = 27 Å andc = 30.56 Å. This is further understood to be composed of a pseudotetragonal cell ofa =b = 5.41 Å. The highT c phase similarly pertains to the orthorhombic structure withc = 36 Å. 相似文献
19.
Z. A. Samoilenko E. I. Pushenko N. N. Ivakhnenko V. N. Varyukhin A. M. Prudnikov R. V. Shalaev 《Technical Physics》2008,53(3):343-347
The effect of white and UV radiation on the phase composition of amorphous CN x films are studied by X-ray diffraction analysis and visible-range spectroscopy. The films have variable-range atomic order and consist of amorphous graphite clusters (30 Å) crystalline clusters (50–100 Å) of graphite, diamond, and carbon nitride phases; and intercluster medium with long-range (1–2 Å) atomic order. It is shown that irradiation of the films by white light facilitates the growth of fine graphite clusters. Irradiation by UV light suppresses the growth of the graphite and carbon nitride phases, favoring the growth of the diamond phase (1.5%). It is demonstrated that a change in the mesoscopic phase composition of the CN x films causes a change in the energy gap width in the visible range from E g = 0.75 eV for the films irradiated by white light to E g = 1.75 eV for those exposed to UV radiation. 相似文献
20.
Toshiaki Murakami 《Phase Transitions》2013,86(4):181-182
Phenylethyl ammonium trichloromercurate exhibits a structural phase transition at 402K Phase I—(402K)→ Phase II This transition has been characterized by differential scanning calorimetry, dielectric measurements and X-ray diffraction. The space groups and the cell parameters of both phases were determined by X-ray diffraction from single crystals and powder samples. Phase I has space group I2 or I2/m, a = 25.88(2) Å, b = 7.792(3) Å; c = 5.971(4) Å; β = 96.14(1)°. Phase II has orthorhombic symmetry, space group Cmm2 or C222 with a = 25.91(1) Å; b = 7.836(5) Å; c = 6.116(4) Å. 相似文献