共查询到20条相似文献,搜索用时 15 毫秒
1.
A. Ladam L. Aldon P.-E. Lippens J. Olivier-Fourcade J.-C. Jumas C. Cenac-Morthe 《Hyperfine Interactions》2016,237(1):51
The electrochemical activity of TiNiSn, TiNi 2Sn and Ti 6Sn 5 compounds considered as negative electrode materials for Li-ion batteries has been predicted from the isomer shift- Hume-Rothery electronic density correlation diagram. The ternary compounds were obtained from solid-state reactions and Ti 6Sn 5 by ball milling. The 119Sn Mössbauer parameters were experimentally determined and used to evaluate the Hume-Rothery electronic density [e av]. The values of [e av] are in the region of Li-rich Li-Sn alloys for Ti 6Sn 5 and outside this region for the ternary compounds, suggesting that the former compound is electrochemically active but not the two latter ones. Electrochemical tests were performed for these different materials confirming this prediction. The close values of [e av] for Ti 6Sn 5 and Li-rich Li-Sn alloys indicate that the observed good capacity retention could be related to small changes in the global structures during cycling. 相似文献
2.
We have employed magnetization measurements, M?ssbauer and ESR
spectroscopic techniques, in order to study the ferromagnetic
insulating (FMI) compound La1-xCaxMnO3 (x=0.175)
doped with 1% 57Fe. We have used two samples; one prepared
in air which has cation vacancies and a second in inert
atmosphere, which is stoichiometric. An abrupt change of the
experimental results is obtained, by all techniques, in the
ferromagnetic insulating regime, in the temperature region of
TO/O//≈60 K, where an orbital rearrangement is
suggested to occur. An analysis of these findings points to an
orbital rearrangement transformation. Ferromagnetic resonance
reveals considerable differences between stoichiometric and cation
deficient samples, indicating anisotropy of the exchange
interactions in the former sample with significant temperature
dependence, most pronounced in the vicinity of TO/O// 相似文献
3.
A. Mokhles Gerami K. Johnston H. P. Gunnlaugsson K. Nomura R. Mantovan H. Masenda Y. A. Matveyev T. E. Mølholt M. Ncube S. Shayestehaminzadeh I. Unzueta H. P. Gislason P. B. Krastev G. Langouche D. Naidoo S. Ólafsson the ISOLDE collaboration 《Hyperfine Interactions》2016,237(1):75
Emission Mössbauer spectroscopy has been utilised to characterize dilute 57Fe impurities in In 2O3 following implantation of 57Mn (T 1/2 = 1.5 min.) at the ISOLDE facility at CERN. From stoichiometry considerations, one would expect Fe to adopt the valence state 3 + , substituting In 3+, however the spectra are dominated by spectral lines due to paramagnetic Fe2+. Using first principle calculations in the framework of density functional theory (DFT), the density of states of dilute Fe and the hyperfine parameters have been determined. The hybridization between the 3d-band of Fe and the 2p band of oxygen induces a spin-polarized hole on the O site close to the Fe site, which is found to be the cause of the Fe2+ state in In 2O3. Comparison of experimental data to calculated hyperfine parameters suggests that Fe predominantly enters the 8b site rather than the 24d site of the cation site in the Bixbyite structure of In 2O3. A gradual transition from an amorphous to a crystalline state is observed with increasing implantation/annealing temperature. 相似文献
4.
We are herewith reporting the 151Eu Mössbauer spectra collected on a polycrystalline powder sample of Eu0.75Y0.25MnO3 from 15 K to room temperature. All the spectra consist of a single line, whose shape and related sample thickness are dependent on the temperature T. The thermal trend of the mean square displacement of Eu ion, obtained from the spectra analysis, clearly reveals a large low-temperature anharmonicity and in concomitance with the onset of the magnetic ordering consists in a linear strong decrease interrupted by two narrow wells at 29.5 K and 40 K. This behavior is interpreted in connection with the transfer of spectral weight from the 120 cm-1 optical phonon to the electromagnonic modes. The T-trend of the central shift shows that Eu3+ electronic ground state in the magnetically ordered phase differs from the one in the paramagnetic state. Finally, the temperature dependence of the hyperfine field under T N gives a contribution to interpret some controversial features regarding the phase-diagram. 相似文献
5.
The parameters of hyperfine interactions in the Bi0.8La0.2FeO3 multiferroic have been measured by Mössbauer spectroscopy in the temperature range of 87–850 K. It has been found that the spatial spin-modulated structure that exists in BiFeO3 is destroyed in the substitution of La for 0.2 mol % of Bi and the homogeneous antiferromagnetic structure appears. The temperatures of the magnetic (Néel temperature, T N = 677 ± 3 K) and ferroelectric (Curie temperature, T C = 773 ± 3 K) transitions and the Debye temperature (Θ = 431 ± 12) have been measured. 相似文献
6.
V. S. Pokatilov V. S. Rusakov A. S. Sigov A. A. Belik M. E. Matsnev A. E. Komarov 《Physics of the Solid State》2017,59(3):443-449
Results of Mössbauer investigations on 57Fe nuclei in multiferroic material Bi57Fe0.10Fe0.85Cr0.05O3 in the temperature range from 5.2 to 300 K are presented. Bulk rhombohedral samples were obtained by solidstate synthesis at high pressure. Mössbauer spectra were analyzed using the model of spatial incommensurate spin-modulated structure of the cycloidal type. Information on the influence of substituting Cr cations for Fe cations on hyperfine spectral parameters was obtained: the shift and quadrupolar shift of a Mössbauer line, and isotropic and anisotropic contributions into the hyperfine magnetic field. The anharmonicity parameter m of the spatial spin-modulated structure increases almost 1.7 times at 5.2 K when BiFeO3 is doped with chromium. The data on m were used for calculation of the uniaxial magnetic anisotropy constants and their temperature dependences for pure and chromium-doped BiFeO3. 相似文献
7.
The structure and magnetic properties of spinel-related Mn4+-doped Li0.5Fe2.5O4 nanocrystalline particles of the composition Li0.5Fe2.25Mn0.1875O4, prepared by milling a pristine sample for different times, were investigated. The average crystallite and particle size, respectively, decreased form ~40 nm to ~10 nm and ~2.5 μm to ~10 nm with increasing milling time from 0 h to 70 h. Rietveld refinement of the XRD data of the non-milled sample show the Mn4+ dopant ions to substitute for Fe3+ at the octahedral B-sites of the spinel-related structure. The Mössbauer spectra of the milled ferrites indicate that more particles turn superparamagnetic with increasing milling time. The Mössbauer data collected at 78 K suggest that while in the non-milled sample the Mn4+ ions substitute for Fe3+ at the octahedral B-sites, this is reversed as milling proceeds with doped Mn4+ ions, balancing Fe3+ vacancies and possibly Li+ ions progressively migrate to the tetrahedral A-sites. This is supported by the slight increase observed in the magnetization of the milled samples relative to that of the non-milled one. The magnetic data suggest that in addition to the increasing superparamagentic component of the milled particles, thermal spin reversal and/or spin canting effects are possible at the surface layers of the nanoparticles. 相似文献
8.
Kiichirou?Koyasu Wilko?Westh?user Marco?Niemietz Jan?Heinen Gerd?Gantef?r 《Applied Physics A: Materials Science & Processing》2009,96(3):679-684
Using time-resolved photoelectron spectroscopy, the decay channels of AuO2− and Au2O2− following photoexcitation with 3.1-eV photons have been studied. For AuO2−, a state with a rather long lifetime of 30 ps has been identified. Its decay path could not be determined but photodesorption
can be excluded. For Au2O2−, the spectra indicate O2 desorption after 3.1-eV photoexcitation on a time scale of 1 ps. While comparing these results on Au
n
O2− with analogous data on Ag
n
O2− clusters, a discernible pattern emerges: for dissociatively bound O2(AuO2−, Ag3O2−), there are long-living excited states which do not decay by oxygen desorption, while for molecular chemisorption (Au2O2−, Ag2O2−, Ag4O2−, Ag8O2−), the 3.1-eV photoexcitation triggers fast O2 desorption with a high quantum yield. 相似文献
9.
Zn–Ni–TiO2 and Zn–TiO2 nanocomposites were prepared by galvanostatic cathodic square wave deposition. X-ray diffraction analysis and scanning electron
microscopy revealed that the occlusion of TiO2 nanoparticles (spherical shaped with diameter between 19.5 and 24.2 nm) promotes the formation of the γ-Ni5Zn21 phase, changes the preferred crystallographic orientation of Zn from (101) and (102) planes to (002), and decreases the particle
size of the metallic matrices. The stability of the nanocomposites immersed in near-neutral 0.05 mold m−3 Na2SO4 solution (pH 6.2) was investigated over 24 h. The initial open circuit potential for the Zn–Ni–TiO2 and Zn–TiO2 coatings were −1.32 and −1.51 V (vs. Hg/Hg2SO4), respectively, and changed to −1.10 and –1.49 V (vs. Hg/Hg2SO4) after 24 h of immersion. Data extracted from the steady state polarization curves demonstrated that the metal–TiO2 nanocomposites have, with respect to the metal coatings, a higher corrosion potential in the case of the Zn–Ni alloy composite;
a lower corrosion potential in the case of Zn-based nanocomposite albeit the predominant (002) crystallographic orientation;
and a lower initial corrosion resistance due to the smaller grain size and higher porosity in the Zn–Ni–TiO2 and Zn–TiO2 nanocomposites. Morphological and chemical analyses showed that a thicker passive layer is formed on the surface of the Zn–Ni–TiO2 and Zn–TiO2 deposits. After 24 h of immersion in the sulphate solution, the Zn–Ni–TiO2 coating has the highest corrosion stability due to the double-protective action created by the deposit’s surface enrichment
in Ni plus the higher amount of corrosion products. 相似文献
10.
J. F. Bengoa N. A. Fellenz M. V. Cagnoli L. A. Cano N. G. Gallegos A. M. Alvarez S. G. Marchetti 《Hyperfine Interactions》2010,195(1-3):5-13
Two Fe/MCM-41 systems, one of them sylilated, were obtained to be used as catalysts in Fischer–Tropsch reaction. They have more than 90% of the iron species located inside the support channels, leading to a narrow crystal size distribution accessible to reactive gases. The samples were characterized by X-ray diffraction, atomic absorption spectroscopy, N2 adsorption, Mössbauer spectroscopy and Fourier transformer infrared spectroscopy. Mössbauer spectroscopy allowed us to demonstrate that the catalytic active species were the same in both catalysts. The only difference between them was the surface hydrophobicity, which decreases the “water gas shift reaction” in the sylilated catalyst. Besides, this solid is more active for hydrocarbon production, with a lower methane yield. 相似文献
11.
Jianhong Wei Qi Zhang Yang Liu Rui Xiong Chunxu Pan Jing Shi 《Journal of nanoparticle research》2011,13(8):3157-3165
Polyaniline (PANI)–TiO2 nanocomposites possessing both nano and microscale structures were prepared through a facile hydrothermal route in the presence
of PANI. The nanopapilla particles were characterized by scanning electron microscopy, transmission electron microscopy, energy
dispersive X-ray analysis, X-ray photoelectron spectra, X-ray diffraction, FTIR spectra, UV–Vis spectroscopy, and N2 adsorption analysis, etc. The results show that the composites possess both nano and microscale structures. The TiO2 nanorods are dispersed on PANI with one end fixed to the surface. The photocatalytic properties of the powders were verified
by the photodegradation of gaseous acetone under UV (λ = 254 nm) and visible-light irradiation (λ > 400 nm). In fact, the photocatalytic effects exhibited by the composite particles were superior to that of pure TiO2 and P25 samples. This excellent behavior is attributed to the structural features of PANI–TiO2 microspheres and the synergistic effect between PANI and TiO2 which facilitates a larger amount of surface active sites. This in turn causes a faster charge separation and slower charge
recombination which results in a more efficient decomposition of gaseous pollutants. 相似文献
12.
S. K. Malik P. L. Paulose R. Nagarajan A. E. Dwight P. P. Vaishnava C. W. Kimball 《Hyperfine Interactions》1987,34(1-4):427-430
A new alloy, having the formula, Co2ScSn, has been prepared. This is found to have the cubic Heusler L21 type structure (a = 6.19A). Magnetization measurements reveal a large drop in magnetization around 270K. Low field ac susceptibility also shows a transition at 268K which we take to be the Curie temperature of the alloy. The magnetic moment at 5K is found to be 0.55 B per cobalt atom.119Sn Mössbauer measurements at 8K show a hyperfine split spectrum with a hyperfine field of about 40 kOe. Attempts to prepare other Co2RSn alloys particularly with R=Lu, were not successful. 相似文献
13.
Halogen-substituted barium indate Ba2In2O5 based brownmillerites Ba1.95In2O4.9F0.1 and Ba1.95In2O4.9Cl0.1 have been synthesized. It has been verified radiographically that the single-phase condition is satisfied. The effect of the substituent ion nature on parameters of the crystalline lattice and lengths of In–O bonds has been revealed. The propensity of the phases under study for hydration and formation of energetically unequal ОН– groups in the structure has been proved. In both the cases of doping, the degree of hydration decreased as compared to barium indate Ba2In2O5, which is caused by the participation of the halide ion in the tetrahedral site of indium. 相似文献
14.
SnO2 powders, doped with various 57Fe contents were prepared by a sol-gel method, and annealed finally at 500 °C and 650 °C. These samples were characterized by Mössbauer spectroscopy, vibrating sample magnetometer (VSM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) to investigate the relationship of magnetic properties, grain sizes, annealing temperatures and Mössbauer parameters. The particle sizes of SnO2 powders reduced to less than 100 nm with the increase of Fe contents up to 5%. Rutile SnO2 was the only phase obtained for all samples. Room temperature Mössbauer spectra suggest the presence of two different paramagnetic iron sites for all samples and one magnetically relaxed species for those samples with the lowest iron concentrations. The magnetization increased with the Fe content, but was reduced for the samples annealed at 650 °C perhaps due to a segregation of α-Fe2O3 doped with tin. 相似文献
15.
V. S. Pokatilov A. S. Sigov A. O. Konovalova 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(3):347-351
Pulse nuclear magnetic resonance (NMR) was applied in studying the effect of 57Fe isotope content in multiferroic BiFeO3 on the shape of NMR spectra at 4.2 K. Strong dependences of the NMR line shape on the isotope content and transverse relaxation time were found. Consideration of these effects on NMR line shape shows that there is an undisturbed (with no anharmonicity effect) space spin-modulated structure of the cycloid type in BiFeO3. The Mössbauer effect was also used to investigate the perovskite BiFeO3 at 650, 295, and 87 K. Experimental spectra allowed us to obtain the distribution of hyperfine fields, which was found to be consistent with studies of the NMR line shape. The local electronic and magnetic states of the iron ion were measured. 相似文献
16.
The painting of a rich Jewish merchant “Bildnis eines jüdischen Kaufmanns” from the Netherlands is dated presumably to the 16th century. After a vivid historical background, i.e. robbed by the Nazis by order of Hermann Göring, it was recently discovered on an Austrian flea market. Different analysis methods were combined to identify the time of the production of this historically interesting looted art. Non-destructive MIMOS II Fe-57 Mössbauer spectroscopy was utilised for mesurements in selected spots. This mainly revealed haematite (α-Fe2O3) in the red curtain. In spots of the brown jacket Mössbauer spectra indicated the presence of mainly Iron(III) in super-paramagnetic oxide or oxide-hydroxide. Consecutively SEM measurements revealed a restoration by partly over-painting. The elementary composition of the pigments was examined by a portable-X-ray fluorescence. μ-XRF analysis for element distribution at different areas was performed. The look into a crack showed Zinc-white at the bottom of the crack. Traces of Titanium-white could be found within some locations on the surface of the painting. In terms of provenance of the artwork, the presence of Zink-white suggests that the painting was painted around the 19th century. Titanium-white indicates a reconstruction during the 20th century, approximately between 1917 and 1958. 相似文献
17.
The formation of an intermediate phase in SrFe12O19/La0.9Ca0.1MnO3 composites was demonstrated for the first time using only Mössbauer spectroscopy. The SrFe12O19/La0.9Ca0.1MnO3 composite was prepared by the two-stage (sol–gel and hydrothermal) synthesis with varying initial conditions. The X-ray diffraction studies showed that the composite consisted of two phases: well-formed structures of manganite La0.9Ca0.1MnO3 and hexagonal ferrite SrFe12O19. It was found that nanocrystalline La0.9Ca0.1MnO3 particles with size d ? 150 nm formed in the composites at the surface of plate-like SrFe12O19 crystallites. The Mössbauer studies showed that the composite contained additional (intermediate) phase La0.9Ca0.1Mn(Fe)O3 that formed at the interface between SrFe12O19 and La0.9Ca0.1MnO3 phases. The intermediate phase concentration increased with the molar content of La0.9Ca0.1MnO3; in this case, the fraction of the surface of SrFe12O19 crystallites coated with La0.9Ca0.1MnO3 increased, which led to the increase in the total area of the interface surface and the intermediate phase concentration. 相似文献
18.
Georges Dénès Abdualhafed Muntasar M. Cecilia Madamba Hocine Merazig 《Hyperfine Interactions》2018,239(1):46
Divalent tin fluorides and chloride fluorides appear to be stable relative to oxidation to tetravalent tin at ambient temperature. X-ray diffraction shows only the line of the tin(II) compound, however the 119Sn Mössbauer spectrum of all tin(II) polycrystalline samples has a small broad peak at ca. 0 mm/s. This is the case of polycrystalline α ?SnF2, while the spectrum of a large single crystal polished sufficiently thin shows only the tin(II) doublet, with no SnO2 peak at 0 mm/s. This shows that there is surface oxidation of each solid particle, to give a thin amorphous layer of SnO2 stannic oxide. However, the Mössbauer peak of SnO2 does not grow with prolonged exposure to air at ambient temperature, therefore it must be assumed that the layer of SnO2 has a passivating effect, however oxidation increases at higher temperatures. We have investigated in this work the passivating effect of a layer of SnO2 in two types of solid solutions: (i) in the fluorite type M1?xSnxF2, where the amount of tin at low x values is not sufficient to provide full coverage of the surface of the particles, and (ii) in the PbClF type doubly disordered solid solution, Ba1?xSnxCl1+yF1?y. It was found that passivation works well in the M1?xSnxF2 solid solution, however most of the time, it does not work so well for Ba1?xSnxCl1+yF1?y where it is strongly dependent on the method of preparation and the bonding strength, as shown by the variation versus the tin(II) recoil-free fraction. 相似文献
19.
Cheng-Fu Yang Hong-Hsin Huang Cheng-Yi Chen Ping-Chih Huang Chien-Chen Diao 《Applied Physics A: Materials Science & Processing》2009,94(1):117-122
In this study, two different thin films, TiO2 thin film and TiO2–W–TiO2 multi-layer thin films (W, tungsten), are prepared by RF magnetron sputtering onto glass substrates. The crystal structure,
morphology, and transmittance of TiO2 and TiO2–W–TiO2 multi-layer thin films are investigated by X-ray diffraction, SEM, and UV-Vis spectrometer, respectively. The amorphous,
rutile, and anatase TiO2 phases are observed in the TiO2 thin film and in the TiO2–W–TiO2 multi-layer thin films. The deposition of tungsten as the inter-layer will have large effect on the transmittance and phase
ratios of rutile and anatase phases in the TiO2–W–TiO2 multi-layer thin films. The crystal intensities of amorous TiO2 will decrease as the tungsten is used as the middle layer in the multi-layer structure. The band gap energy values of TiO2 thin film and TiO2–W–TiO2 multi-layer thin films are evaluated from (αhν)1/2 versus energy plots, and the calculated results show that the energy gap decreases from 3.21 eV (TiO2 thin film) to 3.08∼3.03 EV (TiO2–W–TiO2 multi-layer thin films). 相似文献
20.
I. A. Semerikov I. V. Zalivako A. S. Borisenko K. Y. Khabarova N. N. Kolachevsky 《Journal of Russian Laser Research》2018,39(6):568-574
We propose a method for EIT ground state cooling of 171Yb+ ion, which involves three light fields with detuning on a MHz scale. The steady-state mean vibrational quantum number is calculated to be less than 0.005. Efficient cooling is achievable in a motional-mode frequency range of 2π · (1.5 ± 0.5 MHz). 相似文献