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1.
We synthesized compounds with partial substitution of Cs+ cations in CsH2PO4 by Ba2+ cations. The structural, electron transport and thermodynamic properties of Cs1–2x Ba x H2PO4 (x = 0–0.15) were studied for the first time with the help of a set of physicochemical methods: infrared and impedance spectroscopy, X-ray diffraction and synchronous thermal analysis. The proton conductivity of Cs1–2x Ba x H2PO4 at 50–230°C was investigated in detail by impedance measurements. The formation of solid substitution solutions isostructural with CsH2PO4 (P21/m) is observed in the range of substitution degrees of x = 0–0.1, with a slight decrease in the unit cell parameters and some salt amorphization. The conductivity of disordered Cs1–2x Ba x H2PO4 in the low-temperature region increases by two orders of magnitude at x = 0.02 and increases with an increasing fraction of barium cations by three or four orders of magnitude at x = 0.05–0.1; the superionic phase transition practically disappears. At x = 0.15, heterophase systems based on salts are formed, showing high conductivity and a further decrease in the activation energy of conductivity to 0.63 eV. The conductivity of the high-temperature phase of Cs1–2x Ba x H2PO4 does not change with increasing fraction of the substituent. 相似文献
2.
G. N. Gerasimov M. M. Grekhov V. F. Gromov M. I. Ikim E. Yu. Spiridonova L. I. Trakhtenberg 《Russian Journal of Physical Chemistry B, Focus on Physics》2018,12(4):709-713
The structural characteristics, valence states, and distribution of cerium ions between the components in In2O3–CeO2 and SnO2–CeO2 nanocomposites fabricated using the impregnation method were studied. X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX) were used to show that, during impregnation, cerium ions are not included into In2O3 crystals and are disposed only on their surface in the form of nano-sized crystallites or amorphous clusters. On the other side, under the contact of CeO2 clusters with a surface of SnO2 matrix crystals, cerium ions penetrate into the surface layer of these crystals. In contrast to an In2O3–CeO2 system, where the addition of CeO2 does not affect the conduction activation energy, where cerium oxide is added to SnO2, the observed increase in the resistance of a SnO2–CeO2 composite is accompanied by a sufficient increase in activation energy. These data and the XPS spectra confirm the modification of the surface layers of conductive SnO2 crystals as, a result of the penetration of cerium ions into these layers. 相似文献
3.
X-ray structural and polarization optical investigations have been performed, and birefringence and rotation angles of the
optical indicatrix φ
b
and φ
c
of the K2WO2F4 · 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 · 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]\bar 1 ↔ C2/m → P4/nmm for samples A and m ↔ C2/m → P4/nmm for samples B have been found. The second-order proper ferroelastic phase transition (P
[`1]\bar 1 ↔ C2/m) at T
03 = 270–290 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 ↔ G
2. The irreversible first-order phase transition G
2 → G
1 occurs in a temperature range T
02 ≈ 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 ≈ 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. 相似文献
4.
Organic–inorganic hybrid sample [N(C4H9)4]2Cu2Cl6 was prepared via the reaction between copper chloride and tetrabutylammonium chloride. The compound was characterized by
X-ray powder diffraction, IR, Raman, differential scanning calorimetry (DSC), DTA-TGA analysis and electrical impedance spectroscopy.
DSC studies indicate a presence of one-phase transition at 343 K. The complex impedance of compound [N(C4H9)4]2Cu2Cl6 have been investigated in temperature and frequency ranges 300–380 K and 200 Hz–5 MHz, respectively. The Z′ and Z″ versus frequency plots are well fitted to an equivalent circuit model. The circuits consist of the parallel combination
of bulk resistance R
p and constant phase elements CPE. The frequency dependence of the conductivity is interpreted in term of Jonscher's law: s(w) = sdc + Awn \sigma (\omega ){ } = {\sigma_{\rm{dc}}} + { }A{\omega^n} . The conductivity follows the Arrhenius relation. The variation of the value of these elements with temperatures confirmed
the availability of the phase transition at 343 K detected by DSC and electrical measurements. 相似文献
5.
The results of comparative investigations of singlet-oxygen generation by С60 and С70 fullerenes in tetrachloromethane solutions, aqueous suspensions, and solid-phase powders of fullerenes optically excited by cw diode arrays with different wavelengths and by pulsed xenon lamps with a band filter are presented. The measurements were performed by recording singlet-oxygen phosphorescence at the O2(1Δg)–O2(3Σg) transition (λ = 1270 nm). 相似文献
6.
It has been proved byab initio calculation and theoretical analysis that there exist [N2]2−N2 molecular dimers with D2h symmetry group, and there also exists an electric dipole excimer-like transition a1B2g→a1B3u. The theoretical spectra accord with the experimental results for transition a1B2g→a1B3u. The stimulated emission characteristic of N2 molecular dimer was researched through the microwave excited highly pure nitrogen and the method of amplified spontaneous
emission. The experimental results show that N2 molecular dimer has stimulated emission characteristics when the microwave power is more than 100 W and the N2 pressure is in the range from 260 Pa to 2200 Pa. 相似文献
7.
L. S. Kamzina 《Physics of the Solid State》2017,59(9):1778-1782
Phase transformations in [111]- and [001]-oriented PbMg1/3Nb2/3O3–29PbTiO3 single crystals have been studied using dielectric and optical measurements before and after applying an electric field. It is shown that the subsequence of phase transitions rhombohedral (R)—tetragonal (T)—cubic (C) phases is observed in nonpolarized samples of both orientations as temperature increases. In the [111]-oriented crystal, an additional intermediate monoclinic phase (it is possible, M a ) is induced after preliminary polarization at room temperature and the R–M a –T–C phase transitions are observed on heating. In the [001]-oriented crystal, after its polarization, the monoclinic phase forms instead of the rhombohedral phase even at room temperature and the M a –T–C transitions occur on heating. The results are discussed from the point of view of the existence polar nanoregions with different local symmetries in a glasslike matrix. 相似文献
8.
M. V. Kuznetsov E. V. Shalaeva A. F. Prekul N. I. Shchegolikhina 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(5):628-631
The electronic spectra of the valence band and core levels of the surface of polygrain alloys with the icosahedral structure and the β-(CsCl)-type solid solution of Al50Cu33Fe17 were investigated by X-ray photoelectron spectroscopy (XPS). The obtained XPS spectra of the Al62.5Cu25Fe12.5 alloy, in comparison with those of the crystalline Al50Cu33Fe17 alloy demonstrate narrowing and a decrease in asymmetry of the Fe2p core level and a decrease in the electron state density N(E F ) near the Fermi level, features expected for the poorly conducting icosahedral phase. The XPS data are compared with the estimates of N(E F ) based on the low-temperature specific heat measurements. 相似文献
9.
The atomic structure of crystals of the complex [Eu(NO3)23hmpa] NO3·HQuin , (hmpa – hexamethylphosphortriamide, HQuin – quinaldic acid) characterized by intensive luminescence and triboluminescence has been determined by the X-ray method. The noncentro-symmetric crystals of the compound are rhombic : a = 16.8193(3), b = 12.2877(2), c = 27.6516(5) Å, пр. гр. Pca2(1), Z = 4, ρ calc. . = 1.427 g/сm3. The crystals have a structure of the insular type which is presented by the isolated complex molecules, outer-sphere NO3 ? – groups, and neutral molecules of quinaldic acid. Some structural aspects of formation of the luminescent and triboluminescent properties of the compound were discussed: the role of break planes in the crystal destruction was revealed. 相似文献
10.
L. Pereira A. Morozov M. M. Fraga T. Heindl R. Krücken J. Wieser A. Ulrich 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,56(3):325-334
The temperature dependences of the quenching rate constants of the states
N2 (${\rm C} \ {^{3}{
\rm \Pi }_{u}}${\rm C} \ {^{3}{
\rm \Pi }_{u}} v′=0,1) by N2 (X) and of the state
N2 (${\rm C} \ {^{3}{
\rm \Pi }_{u}} \ v^{\prime}=0${\rm C} \ {^{3}{
\rm \Pi }_{u}} \ v^{\prime}=0) by O2 (X) are studied.
Time-resolved light emission from the gas was analyzed in the temperature
range from 300 K to 210 K keeping the gas at constant density. In case of
quenching by N2 (X), the quenching rate constant for the vibrational
level v′= 0 increases by (13 ±3)% with gas cooling whereas the
quenching rate constant for v′= 1 decreases by (5.0 ±2.5)% in this
temperature range. For quenching by O2 (X), the quenching rate constant
decreases by (3 ±2)% with gas cooling. The temperature variation of
the N2 (C 3Πu v′=0) emission intensity for pure nitrogen
and dry air are calculated using the obtained quenching rate constants and
is compared with the experimental data available in the literature. 相似文献
11.
E. A. Zvereva M. I. Stratan I. L. Shukaev V. B. Nalbandyan A. N. Vasil’ev 《Journal of Experimental and Theoretical Physics》2017,124(4):612-616
A new layered oxide, sodium–cobalt tellurate Na3.70Co1.15TeO6, is synthesized and structurally characterized, and its static and dynamic magnetic properties are studied. This compound has a new monoclinic structure type with quasi-one-dimensional cation ordering in magnetically active layers. This compound is antiferromagnetically ordered at a Néel temperature T N ~ 3.3 K, and the temperature and field dependences of magnetization suggest competing antiferromagnetic and ferromagnetic interactions. EPR spectroscopy reveals complex spin dynamics when temperature changes and the presence of two different paramagnetic centers, which is attributed to the existence of two structurally nonequivalent (regular and antisite) positions for magnetic Co2+ ions. 相似文献
12.
The effect of IIIA metal and transition metalT substitution for Fe on crystal structure, magnetostriction and spontaneous magnetostriction, anisotropy and spin reorientation of a series of polycrystalline Tb0.3 Dy0.7 (Fe0.9 T 0.1)1.95 (T=Mn, Fe, Co, B, Al, Ga) alloys at room temperature were investigated systematically. It was found that the primary phase of the Tb0.3 Dy0.7 (Fe0.9 T 0.1)1.95 alloys is the MgCu2-type cubic Laves phase structure for different substitution. The magnetostrictionλ s decrases greatly for the substitution of IIIA metal, B, Al and Ga, but is saturated more easily for Al and Ga substitution, showing that the Al and Ga substitution is beneficial to a decrease in the magnetocrystalline anisotropy of Tb0.3 Dy0.7 (Fe0.9 T 0.1)1.95 alloys. However, the substitution of transition metal Mn and Co decreases slightly the magnetostrictionλ s . It was also found that the effect of different substitutions on the spontaneous magnetostrictionλ 111 is distinct. The analysis of the Mössbauer spectra indicates that the easy magnetization direction in the {110} plane deviates slightly from the main axis of symmetry for Al and Ga substitution, namely spin reorientation, but it does not change evidently for B, Mn and Co substitution. 相似文献
13.
Jinguang Cheng Yu Sui Yang Wang Xianjie Wang Wenhui Su 《Applied Physics A: Materials Science & Processing》2009,94(4):911-916
Transportation and thermodynamic properties of misfit-layered polycrystalline [Ca2CoO3]0.62[CoO2] were measured in order to clarify the nature of metal– semiconductor transition (MST) at T
MS≈400 K, above which the simultaneous decrease of resistivity and increase of thermopower with temperature give rise to a great
enhancement of thermoelectric power factor up to 1000 K. A first-order phase transition characteristic around T
MS was revealed by anomalies of resistivity, differential scanning calorimetry, and thermal expansion. The first-order characteristic
of the MST can be rationalized from the Virial theorem at an itinerant to localized electron transition in the narrow e
T
band within the [CoO2] plane. Above T
MS, the reduction of the retained delocalized states within the matrix of localized states and the enhancement of charge carrier
effective mass with increasing temperature might account for the considerable enhancement of the thermopower. 相似文献
14.
K.?Sudheendran M.?Ghanashyam?Krishna K.?C.?James?Raju 《Applied Physics A: Materials Science & Processing》2009,95(2):485-492
Bismuth Zinc niobate (Bi1.5Zn1.0Nb1.5O7) thin films were deposited by pulsed laser deposition (PLD) method on fused silica substrates at different oxygen pressures.
The structural, microwave dielectric and optical properties of these thin films were systematically studied for both the as-deposited
and the annealed films at 600°C. The as-deposited films were all amorphous in nature but crystallized on annealing at 600°C
in air. The surface morphology as studied by atomic force microscopy (AFM) reveals ultra-fine grains in the case of as-deposited
thin films and cluster grain morphology on annealing. The as-deposited films exhibit refractive index in the range of 2.36–2.53
(at a wavelength of 750 nm) with an optical absorption edge value of 3.30–3.52 eV and a maximum dielectric constant of 11
at 12.15 GHz. On annealing the films at 600°C they crystallize to the cubic pyrochlore structure accompanied by an increase
in band gap, refractive index and microwave dielectric constant. 相似文献
15.
The resistance of a La1.2Sr1.8Mn2(1–z)O7 single crystal has been studied in magnetic fields from 0 to 90 kOe. The magnetoresistance at temperature T = 75 K, near which a colossal magnetoresistance maximum is observed, has been successfully described in terms of the “spin–polaron” electric conduction mechanism. This value of the colossal magnetoresistance is due to a three-fold increase in the polaron size. The method of separating contributions of various conduction mechanisms to the magnetoresistance developed for materials with activation type of conduction is generalized to compounds in which a metal–insulator transition is observed. It is found that, at a temperature of 75 K, the contribution of the “orientation” mechanism is maximum (≈20%) in a magnetic field of 5 kOe and almost disappears in fields higher than 50 kOe. 相似文献
16.
S. Canulescu T. Lippert A. Wokaun 《Applied Physics A: Materials Science & Processing》2008,93(3):771-778
The mass distributions of the species generated by laser ablation from a La0.6Ca0.4MnO3 target using laser irradiation wavelengths of 193 nm, 266 nm and 308 nm have been investigated with and without a synchronized
gas pulse of N2O. The kinetic energies of the species are measured using an electrostatic deflection energy analyzer, while the mass distributions
of the species were analyzed with a quadrupole mass filter.
In vacuum (pressure 10−7 mbar), the ablation plume consists of metal atoms and ions such as La, Ca, Mn, O, LaO, as well as multiatomic species, e.g.
LaMnO+. The LaO+ diatomic species are by far the most intense diatomic species in the plume, while CaO and MnO are only detected in small
amounts.
The interaction of a reactive N2O gas pulse with the ablation plume leads to an increase in plume reactivity, which is desired when thin manganite films are
grown, in order to incorporate the necessary amount of oxygen into the film. The N2O gas pulse appears to have a significant influence on the oxidation of the Mn species in the plume, and on the creation of
negative ions, such as LaO−,O− and O2−. 相似文献
17.
We report KF-doping work on the recently found ferroelectric material BaTi2O5. The ceramic samples, Ba1-xKxTi2O5-xFx, were synthesized by solid-state reaction of mixed KF and sol–gel-derived BaTi2O5 powders at 1150 °C. An almost pure phase was obtained for nominal composition x≤0.097, while electron probe microanalysis
indicated that the real incorporated K and F contents were less than half of the nominal values. It was observed that KF-doping
is beneficial in enhancing the ceramic density to some extent, which is a key issue in sol–gel-derived BaTi2O5 ceramics, due to a possible liquid-phase sintering mechanism through the presence of melted KF at the sintering temperature.
Scanning electron microscopy images showed that these porous ceramic samples are composed of sub-micron-sized powder aggregates
which, with increasing KF-doping, undergo further agglomeration. Dielectric measurement from room temperature to ∼ 560 °C
showed a broad ferroelectric phase transition, with TC ∼ 430 °C for the undoped sample. As KF-doping increases, TC decreases, and the magnitude of the dielectric constant maximum also displays a decreasing trend. The strongly reduced dielectric
response can be partly understood by regarding the porous ceramic sample as a composite material composed of bulk BaTi2O5 and air, where the porosity has a significant influence on the effective dielectric constant.
PACS 77.84.-s; 77.84.Dy; 81.20.Fw 相似文献
18.
We investigate the temperature dependent of magnetizations, hysteresis properties and present the superconducting phase diagrams of the YBa2Cu3O7–δ (YBCO) by an Ising model within the effective-field theory. We obtain the magnetizations of the YBCO and its components (Cu1, Cu2, O1, O2, O3, O4, Ba, Y, CuO-shell, YBa-core, and total YBCO) versus the reduced temperature and external magnetic field. We find that the copper atoms have two different magnetizations (Cu1 and Cu2) and oxygen atoms have four different magnetizations (O1, O2, O3, O4) but yttrium and barium has one magnetization. The differences in the magnetizations of the copper and oxygen atoms result from the lattice location of them on the YBCO lattice. The magnetization of the Cu1 atoms is the lowest and the yttrium is highest than those of the others; hence magnetizations of the YBCO increase from the corner to inner of the orthorhombic YBCO lattice. We also find that the YBa-core, yttrium and barium atoms of the YBCO exhibit superconductivity behaviors. Therefore, Y–Ba core, yttrium and barium atoms have the superconducting phase diagram and it has Meissner, vortex, and normal states. It is also found that the upper critical coercive field (Hc2) and the critical vortex temperature (Tv) of the Ba are high than those of the Y and YBa-core. 相似文献
19.
The broadening and shift coefficients of more than 100 absorption lines of the ν2 + ν3 band of water vapor that are induced by the pressure of helium are measured and calculated. The broadening and shift coefficients are obtained from analysis of the room-temperature absorption spectra of an H2O-He mixture measured with a resolution of 0.007 cm?1 on a Fourier spectrometer in a large range of helium pressures. The specific features in the rotational dependence of the line center shifts are determined, which, in contrast to the broadening induced by other gases, are mainly positive. The calculated coefficients of the line broadening and shift of line centers are determined by a semiclassical method. An unusual dependence of the shift coefficients is explained by the rotational dependence of the intermolecular isotropic interaction potential. 相似文献
20.
The IR absorption spectra of cryosolutions of chloroform, dimethyl ether, and their mixtures in liquefied krypton have been measured. It has been shown that, in solutions of mixtures, Cl3CH…O(CD3)2 complexes with a weak hydrogen bond are formed. The spectral characteristics of individual absorption bands that refer to proton donors and to proton acceptors have been determined. From temperature measurements of the integrated intensities of the bands of monomers and of the complex (T ~ 120–160 K), the enthalpy of the complex formation has been estimated. The measurement data have been analyzed in comparison with the results of ab initio calculations in terms of the МР2/6-311++G(2df, 2pd) approximation. The analysis has been done taking into account peculiarities of the dipole moment function of chloroform and possible effects of the anharmonic interaction between the С–Н stretching vibration and the overtone of the Cl–C–H bending vibration. 相似文献