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1.
The influence of Rh doping on the structure of Sr2RuO4 has been investigated using neutron powder diffraction methods. The metallic Ru rich compounds adopt a regular K2NiF4-type structure, space group I4/mmm, with Ru-O-Ru bond angles of 180°. The structures of the nonmetallic Rh rich compounds crystallise in space group I4/acd and are characterised by tilting of the MO6 octahedra reducing the Ru-O-Ru angle to about 160°. Irrespective of Rh content the MO6 polyhedra are not regular octahedra but are elongated along the c direction. The temperature dependence of the structure of Sr2Ru0.9Rh0.1O4 was investigated and revealed this elongation to be weakly temperature dependent. 相似文献
2.
Chul Kim C.S. Leem Y.K. Kim W.S. Jung H.Y. Choi R.G. Moore C. Kim 《Journal of Physics and Chemistry of Solids》2011,72(5):556-558
We report angle-resolved photoemission spectroscopy studies on Sr2RuO4. We observe multiple-bosonic mode coupling in the α and β band dispersions. To extract the self-energy from the data for which the usual fitting methods do not work well, we propose a scheme that exploits the relation between the spectral intensity and self-energy, termed as relative self-energy. The relative self-energy obtained in that way contains important features of the self-energy. We observe not only the features that can be obtained from the band dispersions but also additional features that were not seen. 相似文献
3.
H. Hagemann V. D'Anna S. Gomes G. Renaudin K. Yvon 《Journal of Physics and Chemistry of Solids》2011,72(4):286-289
The structural and vibrational properties of the isostructural compounds Ca2FeH6 and Sr2RuH6 are determined by periodic DFT calculations and compared with their previously published experimental crystal structures as well as new experimental vibrational data. The analysis of the vibrational data is extended to the whole series of alkaline-earth iron and ruthenium hydrides A2TH6 (A=Mg, Ca, Sr; T=Fe, Ru) in order to identify correlations between selected frequencies and the T-H bond length. The bulk moduli of Ca2FeH6 and Sr2RuH6 have also been determined within DFT. Their calculated values prove to compare well with the experimental values reported for Mg2FeH6 and several other compounds of this structure. 相似文献
4.
H. Kambara S. Kashiwaya H. Yaguchi Y. Asano Y. Tanaka Y. Maeno 《Physica C: Superconductivity and its Applications》2009,469(15-20):1030-1033
We have investigated the transports of micro-fabricated sample of 3-K phase superconductivity (Tc 3 K) in Sr2RuO4–Ru eutectic system in order to clarify the pairing symmetry. Up to now, pure Sr2RuO4 (Tc = 1.5 K: 1.5-K phase) is widely recognized to be a spin-triplet odd-parity superconductor. However, the enhancement mechanism of Tc up to 3 K and the pairing symmetry of the 3-K phase have not been cleared yet. By using micro fabrication technique with focused ion beam, we have succeeded to extract individual superconducting channels for the 3-K phase in which only a few pieces of Ru inclusions are contained. Multiple kink structures observed in differential resistance–current (dV/dI − I) characteristics indicate serially connected superconducting filaments in the 3-K phase. We confirm that the 3-K phase is an odd-parity superconductor similar to pure Sr2RuO4 from the monotonous temperature dependence of the critical currents. In addition, we observed a quite unusual hysteresis in dV/dI − I below 2 K, which suggests the internal degrees of freedom in the superconducting state: the most probably the chiral p-wave state. 相似文献
5.
Kenji Ishida Hiroshi Murakawa Yoshio Kitaoka Yoshiteru Maeno 《Journal of Physics and Chemistry of Solids》2008,69(12):3108-3114
We review our nuclear-magnetic resonance (NMR) and nuclear-quadrupole-resonance (NQR) studies in superconducting Sr2RuO4, which have been performed in order to investigate the gap structure and the pairing symmetry in the superconducting state and magnetic fluctuations in the normal state. The spin-lattice relaxation rate (1/T1) of a high-quality sample with shows a sharp decrease without a coherence peak just below Tc, followed by a T3 behavior down to 0.15 K. This result indicates that the superconducting gap in pure Sr2RuO4 is a highly anisotropic character with a line-node gap. The Knight shift, which is related to the spin susceptibility, is unchanged in the superconducting state irrespective of the direction of the applied fields and various magnitude of the field. This result strongly suggests that the superconducting pairs are in the spin-triplet state, and the spin direction of the triplet pairs is considered to be changed by small fields of several hundred Oe. 相似文献
6.
K.Z RushchanskiiH Haeuseler D.M Bercha 《Journal of Physics and Chemistry of Solids》2002,63(11):2019-2028
For the compounds FeGa2S4 and NiGa2S4 band structure calculations have been performed by the ab initio plane wave pseudo-potential method. The valence charge density distribution points to an ionic type of chemical bonding between the transition metal atoms and the ligand atoms. Two models for the pseudo-potentials are used to calculate the band structures: (a) only s and p electrons and (b) also the d-shells of the transition metal atoms are included in the pseudo-potentials. The differences between these two cases of band structures are discussed. Energy gap formation peculiarities are analysed for both crystals. Zak's elementary energy band concept is demonstrated for the energy spectra of the considered crystals. 相似文献
7.
Ran Pang Chengyu Li Lili Shi Qiang Su 《Journal of Physics and Chemistry of Solids》2009,70(2):303-306
By introducing the Y3+ into Sr2P2O7:Eu2+, we successfully prepared a kind of new phosphor with blue long-lasting phosphorescence by the high-temperature solid-state reaction method. In this paper, the properties of Sr2P2O7:Eu2+,Y3+ were investigated utilizing XRD, photoluminescence, luminescence decay, long-lasting phosphorescence and thermoluminescence (TL) spectra. The phosphor emitted blue light that was related to the 4f65d1-8S7/2 transition of Eu2+. The bright blue phosphorescence could be observed by naked eyes even 8 h after the excitation source was removed. Two TL peaks at 317 and 378 K related to two types of defects appeared in the TL spectrum. By analyzing the TL curve the depths of traps were calculated to be 0.61 and 0.66 eV. Also, the mechanism of LLP was discussed in this report. 相似文献
8.
A method is described which is capable of simulating disorder across a range of composition. It is used to study the disorder of iron and aluminium on the octahedral and tetrahedral cation sites in the Brownmillerite phase Ca2FexAl2−xO5. The arrangements with the lowest lattice energies are those that maximize the number of Fe3+ on octahedral sites throughout the composition range. An exchange of one Fe3+ with one Al3+, which results in a decrease in the number of iron ions on octahedral sites, increases the lattice energy by an amount that is dependent on x but is independent of the number of exchanges. The exchange of trivalent cations also results in an expansion in the b lattice direction, accompanied by a decrease in the a and c directions across the full range of composition. 相似文献
9.
By using diamond anvil cell (DAC), high-pressure Raman spectroscopic studies of orthophosphates Ba3(PO4)2 and Sr3(PO4)2 were carried out up to 30.7 and 30.1 GPa, respectively. No pressure-induced phase transition was found in the studies. A methanol:ethanol:water (16:3:1) mixture was used as pressure medium in DAC, which is expected to exhibit nearly hydrostatic behavior up to about 14.4 GPa at room temperature. The behaviors of the phosphate modes in Ba3(PO4)2 and Sr3(PO4)2 below 14.4 GPa were quantitatively analyzed. The Raman shift of all modes increased linearly and continuously with pressure in Ba3(PO4)2 and Sr3(PO4)2. The pressure coefficients of the phosphate modes in Ba3(PO4)2 range from 2.8179 to 3.4186 cm−1 GPa−1 for ν3, 2.9609 cm−1 GPa−1 for ν1, from 0.9855 to 1.8085 cm−1 GPa−1 for ν4, and 1.4330 cm−1 GPa−1 for ν2, and the pressure coefficients of the phosphate modes in Sr3(PO4)2 range from 3.4247 to 4.3765 cm−1 GPa−1 for ν3, 3.7808 cm−1 GPa−1 for ν1, from 1.1005 to 1.9244 cm−1 GPa−1 for ν4, and 1.5647 cm−1 GPa−1 for ν2. 相似文献
10.
J.H. Jung 《Solid State Communications》2005,133(2):103-107
We have reported the Raman scattering and infrared absorption results on a t2g orbital ordered Ca2RuO4. At 10 K, a strong and clear peak was observed in Raman scattering near 1360 cm−1 with x′x′ geometry. In contrast to optic phonon modes, the peak does not show any frequency shift but rapidly decreases with increasing temperature. In addition, the peak is not observed in infrared absorption measurement. By comparing the previous Raman scattering results for several transition metal oxides, we have discussed the possible origins and ambiguities of the intriguing peak in Ca2RuO4. 相似文献
11.
Hai-Bo Yang Ying Lin Jian-Feng Zhu Fen Wang 《Journal of Physics and Chemistry of Solids》2009,70(1):55-275
The sintering behavior, microstructures, and microwave dielectric properties of Ca2Zn4Ti15O36 ceramics with B2O3 addition were investigated. The crystalline phases and microstructures of Ca2Zn4Ti15O36 ceramics with 0-10 wt% B2O3 addition were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The sintering temperature of Ca2Zn4Ti15O36 ceramic was lowered from 1170 to 930 °C by 10 wt% B2O3 addition. Ca2Zn4Ti15O36 ceramics with 8 wt% B2O3 addition sintered at 990 °C for 2 h exhibited good microwave dielectric properties, i.e., a quality factor (Qf) 11,400 GHz, a relative dielectric constant (εr) 41.5, and a temperature coefficient of resonant frequency (τf) 94.4 ppm/°C. 相似文献
12.
Photocatalytic activity of Nb2O5/SrNb2O6 heterojunction on the degradation of methyl orange 总被引:1,自引:0,他引:1
Jingcheng Xing Zhichao Shan Jianjiang Bian Wendeng Wang 《Journal of Physics and Chemistry of Solids》2008,69(1):23-28
The pure SrNb2O6 powders were prepared at 1400 °C by a conventional solid-state method and characterized by X-ray powder diffraction and UV-vis diffuse reflection spectrum. The powders of Nb2O5 and SrNb2O6 were ball-milled together and annealed to form the Nb2O5/SrNb2O6 composite. Photocatalytic activities of the composites were investigated on the degradation of methyl orange. The results show that the proportion of Nb2O5 to SrNb2O6 and the annealing temperature greatly influence the photocatalytic activities of the composites. The best photocatalytic activity occurs when the weight proportion of Nb2O5 to SrNb2O6 is 30% and the annealing temperature is 600 °C. The tremendously enhanced photocatalytic activity of the Nb2O5/SrNb2O6 composite compared to Nb2O5 or SrNb2O6 is ascribed to the heterojunction effect taking place at the interface between particles of Nb2O5 and SrNb2O6. The powders also show a higher photocatalytic activity than commercial anatase TiO2. 相似文献
13.
We have calculated the band structure of Ca3Co2O6 and Ca3CoNiO6 by using the self-consistent full-potential linearized augmented plane-wave method within density function theory and the generalized gradient approximation for the exchange and correlation potential. The spin-orbit interaction is incorporated in the calculations using a second variational procedure. The relation of these band structure calculations to thermoelectric transport is discussed. The results illustrate that transport is highly anisotropic with much larger mobility in the a-b plane than out of the a-b plane, and the introduction of Ni in Ca3Co2O6 alters its electronic structure and its thermoelectric transport properties. 相似文献
14.
Elaine A Moore Hisham M Widatallah Frank J Berry 《Journal of Physics and Chemistry of Solids》2002,63(3):519-523
The defect structure of lithiated tin- and titanium-doped α-Fe2O3 has been assessed using interatomic potential calculations. Of the models considered for lithiation, a model in which Li+ occupies an interstitial site balanced by the reduction of Fe3+ to Fe2+ on an Fe3+ site was found to be more favourable than the substitution of Li+ on an Fe3+ octahedral site balanced by an O2− vacancy. Insertion of lithium into the interstitial site between two adjacent M4+ ions was particularly favourable. The calculated lattice parameters decrease on lithiation as has been observed experimentally. 相似文献
15.
Yong Sun Won 《Journal of Physics and Chemistry of Solids》2010,71(12):1742-1745
The supercells of pure and Eu-doped Sr2SiO4 were theoretically analyzed by density functional theory (DFT) calculations to investigate the typical two-peak emission of Sr2SiO4:Eu2+, which originates from two different Sr2+ (or Eu2+) sites in the Sr2SiO4 host structure. The Perdew-Wang generalized-gradient approximation (GGA) functional and the double numerical plus d-functions (DND) basis set with effective core potentials (ECP) were employed in the calculations of electronic properties. The electron transfer between Eu2+ ions placed at two different crystallographic Sr2+ sites was understood based on the accurate assignment of deconvoluted peaks of the two-peak emission to their corresponding crystallographic sites. This study ought to be instructive as a basic guideline to improve the color chromaticity of Sr2SiO4:Eu2+ for use in white light emitting diodes (WLEDs). 相似文献
16.
Yuki Obukuro Hiroyuki Nakamura Kenji Obata Shigenori Matsushima Masao Arai Kenkichiro Kobayashi 《Journal of Physics and Chemistry of Solids》2011,72(12):1477-1481
The electronic structure of Sr2Bi2O5 is calculated by the GGA approach. Both of the valence band maximum and the conduction band minimum are located at Γ-point. This means that Sr2Bi2O5 is a direct band-gap material. The wide energy-band dispersions near the valence band maximum and the conduction band minimum predict that holes and electrons generated by band gap excitation have a high mobility. The conduction band is composed of Bi 6p, Sr 4d and O 2p energy states. On the other hand, the valence band can be divided into two energy regions ranging from −9.5 to −7.9 eV (lower valence band) and from −4.13 to 0 eV (upper valence band). The former mainly consists of Bi 6s states hybridizing with O 2s and O 2p states, and the latter is mainly constructed from O 2p states strongly interacting with Bi 6s and Bi 6p states. 相似文献
17.
Multi-color long lasting phosphorescent (LLP) phenomenon in β-Zn3(PO4)2:Mn2+,Zr4+ was systematically investigated. It is found that the red (λEm=616 nm) LLP performance of Mn2+ such as brightness and duration is largely improved, and that the blue (λEm=475 nm) LLP of Zr4+ with lower intensity appears when Zr4+ ions are co-doped into the matrix. The fluorescence, phosphorescence and thermoluminescence (TL) spectra show that Mn2+ ion is solely expected as a luminescent center, while Zr4+ ion not only acts as a luminescent center, but also induces an electron trap (TrapZr) associated with a TL peak at 344 K. The trap depth for TrapZr is 0.25 eV, while that for the intrinsic trap is 0.38 eV, associated with a dominant peak at 385 K for Zn3(PO4)2:Mn2+. The Zr4+-induced trap with suitable depth is responsible for the improvement of the red LLP of Mn2+ ion and the appearance of the blue LLP of Zr4+ ion. The LLP mechanism is also investigated. 相似文献
18.
J. Raittila T. Salminen K. Schlesier 《Journal of Physics and Chemistry of Solids》2006,67(8):1712-1718
Double perovskite Sr2FeMoO6 powders with small crystallite size have been synthesised with citrate-gel method. The starting solution pH was varied between 1.5 and 9.0 resulting in large differences in the phase composition and ordering of B′/B″ sites. The samples prepared at 975 °C had crystallite sizes under 40 nm whereas crystallite sizes of the samples prepared at 1050 °C were between 78 and 239 nm. The XRD patterns were refined with spacegroup I 4/m, which gave good results for both batches, although clearly better results were obtained with monoclinic P 21/n spacegroup for the 975 °C batch. The ordering and the saturation magnetization agreed well with each other after treatment at 1050 °C, but the samples prepared at 975 °C had a strongly reduced saturation magnetization from that given by the ordering. 相似文献
19.
Using first-principles electronic structure theory, we have calculated defect formation energies and defect transition levels in CuInSe2 and CuGaSe2. We show that (i) it is easy to form Cu vacancies in CuInSe2, and (ii) it is also relatively easy to form cation antisite defects (e.g. InCu) for this ternary compound. Consequently, defect pairs such as (2VCu+InCu) have a remarkably low formation enthalpy. As a result, the formation of a series of Cu-poor compounds (CPCs) such as CuIn5Se8 and CuIn3Se5, is explained as a repeat of (2VCu+InCu) pairs in CuInSe2. The very efficient p-type self-doping ability of CuInSe2 is explained by the easy formation of the shallow Cu vacancies. The electrically benign character of the natural defect in CuInSe2 is explained in terms of an electronic passivation of the by . For CuGaSe2, we find that (i) the native acceptor formation energies and transition energy levels are similar to that in CuInSe2, but the donor formation energy is larger in CuGaSe2. (ii) The GaCu donor level in CuGaSe2 is deeper than InCu donor level in CuInSe2, therefore, GaCu behaves as an electron trap in CuGaSe2, even when it is passivated by VCu. We have also calculated the band alignment between the CPCs and CuInSe2, showing that it could have significant effect on the solar cell performance. 相似文献
20.
We present the infrared and Raman study of the optical phonon modes of the defective compounds ZnGa2Se4 and ZnGa2S4. Most of the compounds have been found to crystallize in the thiogallate structure (defect chalcopyrite) with space group where all cations and vacancies are ordered. For some Zinc compounds a partially disordered cationic sublattice with various degrees of cation and vacancy statistical distribution, which lead to the higher symmetry (defect stannite), has been reported. For ZnGa2Se4 we have found three modes of A symmetry, showing Raman activity only. In addition, we have observed each five modes of B and E symmetry, showing infrared as well as Raman activity. The number of modes and their symmetry assignment, based on polarized measurements, clearly indicate space group for the investigated crystals of ZnGa2Se4.Regarding ZnGa2S4 we have found three modes exclusively showing Raman activity (2A⊕1B1), and only eight modes showing infrared as well as Raman activity (3B2⊕5E). The assignment of the modes has been derived by analyzing the spectral positions of the vibrational modes in comparison to a number of compounds. From the number and symmetry assignment of the optical phonon modes we confirm that ZnGa2S4 most likely crystallizes in space group . 相似文献