共查询到20条相似文献,搜索用时 15 毫秒
1.
S. Sugai T. Adachi K. Sugiura T. Takahashi K. Obara Y. Takayanagi Y. Koike 《Journal of Superconductivity and Novel Magnetism》2009,22(3):313-317
The superconductivity depression mechanisms at x≈1/8 in La2−x
Ba
x
CuO4 and Zn substitution in La2−x
Sr
x
CuO4 were investigated by Raman scattering. About 80% of low-energy electronic states are two-dimensional at x≈1/8 and form the Fermi arc around (π/2,π/2). The low-energy states are composed of the resonant peak relating to the insulator–metal transition and the polaron states
of the B
3u phonons. Zn substitution depresses the resonant peak, while the LTT structure depresses the polaron states. The superconductivity
is suppressed if one of them is reduced. 相似文献
2.
Tribedi Bora P. Saravanan S. Ravi 《Journal of Superconductivity and Novel Magnetism》2013,26(5):1645-1648
LaCr1?x Fe x O3 (x=0, 0.4, 0.45, 0.6 and 1.0) have been prepared in single phase form with Pbnm space group. The x=0 sample exhibits antiferromagnetic (AFM) transition at Néel temperature T N =290 K and it is found to reduce with increase in doping concentration up to x=0.45. Magnetization reversal below a compensation temperature of 100 K was observed in the x=0.45 sample and it is explained in terms of competition between two AFM interactions and associated magnetic anisotropy. Exchange bias was observed in the x=0.45 sample and the temperature dependence of exchange bias field and vertical magnetization shift were analyzed. 相似文献
3.
Rocksalt-type (Ni1–x
Li
x
)O (x=0.1 and 0.2) was synthesized at 1350° C in air and its electrical resistivity (R) was measured under various relative humidities (H). R increases with increasing H in the range 0H79%, reaches a maximum value, then decreases in the range 79%<H100%. The increase in R is explained by an electron boundary layer model. On the other hand, the decrease in R is explained by ionic conductivity. 相似文献
4.
V. I. Pet’kov M. V. Sukhanov A. S. Shipilov V. S. Kurazhkovskaya E. Yu. Borovikova I. Yu. Pinus A. B. Yaroslavtsev 《Inorganic Materials》2014,50(3):263-272
The LiZr2(AsO4)3 arsenate and LiZr2(AsO4) x (PO4)3 ? x solid solutions have been prepared through precipitation followed by heat treatment, and characterized by X-ray diffraction, X-ray structure analysis, IR spectroscopy, and impedance spectroscopy. We have established conditions for the crystallization of the arsenate and a continuous series of arsenate phosphate solid solutions (0 ≤ x ≤ 3), which have been obtained as two polymorphs: monoclinic and hexagonal. Using the Rietveld method, we have refined the crystal structures of the polymorphs of LiZr2(AsO4)3 (sp. gr. P21/n, a = 9.1064(2), b = 9.1906(2), c = 12.7269(3) Å, β = 90.844(2)°, V =1065.03(5) Å3, Z = 4; sp. gr. R $\bar 3$ c, a = 9.1600(4), c = 22.9059(13) Å, V = 1664.44(14) Å, Z = 6) and LiZr2(AsO4)1.5(PO4)1.5. Their structural frameworks are built up of AsO4 tetrahedra—or (As,P)O4 tetrahedra occupied by arsenic and phosphorus atoms at random—and ZrO6 octahedra, with the lithium atoms in between. The ionic conductivity of the materials has been measured. The cation conductivity of monoclinic LiZr2(AsO4) x (PO4)3 ? x with 0 ≤ x ≤ 1 has been shown to exceed the conductivity of lithium zirconium phosphate. 相似文献
5.
SrBi2(Nb1 – x
V
x
)2O9 (0 x 0.3 in molar ratio) ceramics have been fabricated via conventional sintering at elevated temperatures. Interestingly sintering the pellets in the 1320–1470 K temperature range yielded partially grain oriented ceramics. The orientation factor (f) monitored via X-ray powder diffraction studies was found to increase with increasing V2O5 content and reached 83% for x = 0.3. The increment in (f) was not that significant with increase in sintering temperature and its duration. The microstructural studies suggest that V2O5 has a truncating effect on the abnormal platy growth of SBN grains. The dielectric constant (r) and loss (D) measurements as functions of both temperature and V2O5 content have been carried out along the directions parallel (rp) and perpendicular (rn) to the cold pressing axis of the pellet. The anisotropy (rn/rp) associated with r was found to be 1.11 at 300 K and 2.1 at the Curie temperature, (T
c) respectively. Different dielectric mixture formulae that were employed to analyze the effective dielectric constants of these samples with varying porosity confirmed that the experimental value of r was comparable with that obtained using Wiener's formula. Impedance spectroscopy was employed to rationalize the electrical behavior of these ceramics. The pyroelectric coefficients along the directions parallel and perpendicular to the pressing axis of the grain oriented (83%) SBN ceramic at 300 K were 0.13145 mC/m2K and 0.26291 mC/m2K respectively. The ferroelectric properties of these grain-oriented ceramics were better in the direction perpendicular to the pressing axis than those in the parallel direction. 相似文献
6.
《Scripta Metallurgica》1984,18(11):1257-1261
Positional and orientational ordering of Ga pairs were observed in the La-Ga system, which leads to the formation of a new compound, LaGa4, having an orthorombic cell, space group Pmmm, and lattice parameters of a0 = 0.434nm and c0 = 0.441nm. A structural relation exists between LaGa2, La(1−x) Ga2(1+x), LaGa4, LaGa6 and Ga and the structure obtained depends on the degree of substitution of the La atoms by Ga-like molecules. 相似文献
7.
A. S. Saidov É. A. Koshchanov A. Sh. Razzakov Sh. K. Ismailov 《Technical Physics Letters》1999,25(12):986-987
Structures comprising Si-Si1−x
Gex-(Ge2)1−x
(InP)x with an intermediate Si1−x
Gex buffer layer were grown on silicon substrates. Morphological examinations, scanning patterns and diffraction spectra, and
also the electrophysical and luminescence properties of the heterostructures were used to show that the crystal perfection
of these structures depends on the choice of liquid-phase epitaxy conditions.
Pis’ma Zh. Tekh. Fiz. 25, 37–40 (December 26, 1999) 相似文献
8.
Fermin Ak Fatma Güçlü Buket Saatçi Nazmiye Kervan Selçuk Kervan 《Journal of Superconductivity and Novel Magnetism》2016,29(2):409-416
Crystal structure and magnetic properties of the Co2Mn1?x V x Sb (0 ≤ x ≤ 1) Heusler compounds have been studied by X-ray powder diffraction (XRD), magnetometric measurements, and full-potential linearized augmented plane wave (FP–LAPW) method. All compounds crystallize in a cubic Cu2MnAl-type crystal structure with the space group Fm–3m. The samples for x<0.8 have the Curie temperatures above room temperature, while the Curie temperature is observed at 68 K for the sample with x = 0.8. The saturation magnetization at 5 K decreases linearly with increasing vanadium concentration x. The values of the saturation magnetization obtained by FP–LAPW–local density approximation (LDA) calculations are in better agreement with the experimental results compared with the results obtained by FP–LAPW–generalized gradient approximation (GGA) calculations. 相似文献
9.
In order to lower the temperature required to density (Ba1–x
Sr
x
) (Ti0.9Zr0.1) O3 (BSTZ-series) and to avoid the formation of a low dielectric constant phase, copper oxide is added as liquidphase promotor after BSTZ-series are calcined. Thea-axis lattice constant at room temperature elongates with both increasing amount of CuO added and higher sintering temperature, while thec-axis lattice constant elongates only slightly under the same condition. The dielectric constant increases with sintering temperature. However, for different amounts of CuO added, the dielectric constant increases with increasing amount of CuO at lower sintering temperatures (below 1100°C). When a higher sintering temperature is used (above 1200°C), the dielectric constant reaches a maximum at 1 wt % CuO added, and decreases slightly on further addition of CuO. 相似文献
10.
E. P. Zaretskaya I. A. Victorov V. F. Gremenok A. V. Mudryi 《Technical Physics Letters》2001,27(1):49-51
Single-phase films of CuInS2x Se2(1−x) solid solutions with a chalcopyrite structure were deposited by laser evaporation of CuInS2x Se2(1−x) crystal targets (0≤x≤1). The structural and optical characteristics of the films depend on the chalcogen concentrations. 相似文献
11.
M. Kh. Balapanov R. Kh. Ishembetov K. A. Kuterbekov T. N. Nurakhmetov E. K. Urazaeva R. A. Yakshibaev 《Inorganic Materials》2014,50(9):930-933
This paper presents an experimental study of the electronic thermoelectric power as a function of copper content for Li x Cu(2?x)?δS (x ≤ 0.25) electronic-ionic mixed conductors. Using a vacancy model for lattice defects, we calculate their electronic thermoelectric power as a function of x. By adjusting the hole effective mass, we reach satisfactory agreement with experimental data. 相似文献
12.
Donald G. S. Chuah R. Ratnalingam R. J. Seward 《Journal of Low Temperature Physics》1978,31(1-2):153-173
The thermal conductivity and electrical resistivity of the tin-lead alloy system Sn
x
Pb1 – x
(x = 0.85, 0.7 0.5 0.3) were measured in the temperature range 7–300 K. The thermal conductivity was analyzed at temperature T 20K, assuming 1//T+Tn, where , , and n are constants. The analysis shows that n < 2, and not n 2, which would be expected for a normal pure metal. The electrical resistivities could be represented by a T
5 relation for temperatures up to about 60 K. The characteristic temperature
R
appears to decrease with increasing weight percent of lead. The total Lorenz functions were high, indicating the presence of phonon conductivity. The phonon conductivity
g
appears to vary with T, and can be represented by g=a/Tn (a > 0) and n2.Work supported by the Universiti Sains Malaysia. 相似文献
13.
S. Musić M. Lenglet S. Popović B. Hannoyer I. Czakó-Nagy M. Ristić D. Balzar F. Gashi 《Journal of Materials Science》1996,31(15):4067-4076
The solid solutions (CrxFe1–x)2O3, 0 x 1, were prepared by traditional ceramic procedures. The samples were characterized using X-ray diffraction, Mössbauer, Fourier transform infra-red (FT-IR) and optical spectroscopic measurements. In the whole concentration range two phases exist phase F, -(CrxFe1–x)2O3, which is isostructural with -Fe2O3 and phase C, which is closely related to Cr2O3. Phase F exists in samples heated up to 900°C, for 0 x 0.95. Phase C exists from x0.27 to x=1 for samples heated up to 900°C and from x0.65 to x=1 for samples heated up to 1200 °C. For samples heated up to 900 °C, the solubility limits were 27.5 ± 0.5 mol% of Cr2O3 in -Fe2O3 and 4.0 ± 0.5 mol % of -Fe2O3 in Cr2O3. For the samples heated at 1200 °C the diffraction peaks for the F and C phases in the two phase region were severely overlapped and thus the solubility limits could not be determined accurately as for previous samples. 57Fe Mössbauer spectra of the samples heated up to 1200 °C showed significant broadening of spectral lines and a gradual decrease of the hyperfine magnetic field with increase of x up to 0.50. For x0.7, a paramagnetic doublet with collapsing sextet was observed. The spectra were interpreted in terms of an electronic relaxation effect; however, an agglomeration of iron ions which would contribute to the superparamagnetic effect could not be excluded. The FT-IR spectra showed transition effects in accordance with the X-ray diffraction results. The most intense absorption bands, observed for the samples heated up to 1200 °C, were located at 460 and 370 nm (22 000 and 27 000cm–1) for x 0.5, 500 and 360 nm for x < 0.3, and might be correlated with the strong enhancement of the pair transitions through antiferromagnetic interactions. The intensification of the 6A1 4T1 Fe3+ ions in all spectra and the development of the absorption at 13000 cm–1 due to a metal-metal charge transfer (Cr3+ Fe3+) transition, might be explained by exchange coupling which has been observed in some spinel compounds. 相似文献
14.
We performed Raman measurements at 18 K and pressures up to 25 GPa in order to construct a tentative phase diagram of the (N
2)1–x
:(O
2)x
–system at low temperatures. We varied the composition of the mixed system over the whole concentration range. Here we focused on the systems with high nitrogen concentration and pressures above 2 GPa. It is known that at room temperature oxygen is highly solvable in the –phase of N
2. The experimental results show that oxygen suppresses the disorder–order transition –N
2. 相似文献
15.
《Materials Letters》2003,57(16-17):2466-2471
The pseudobinary thermoelectric alloys (PbTe)1−x–(SnTe)x (0≤x≤0.4) doped with 0.02 mol% Ag concentration were prepared by pressureless sintering (PS), and their properties were optimized to fit the preparation of functionally graded materials (FGM) with gradient composition. The calculation shows that the FGM can raise the maximal power output to approximately 200.0 (W m−2), at least 21% greater than that of the best monolithic alloys (PbTe)0.6–(SnTe)0.4. The measurement shows that the maximum power output of FGM is about 175.0 (W m−2), and at least increases by about 16% as compared to those of any monolithic materials (PbTe)1−x–(SnTe)x (0≤x≤0.4) without or with different Ag concentration doping. 相似文献
16.
The structure of a scandium gallium oxide single crystal grown by the Czochralski process from a charge of composition Ga1.5Sc0.5O3 is determined by x-ray diffraction. The structure is shown to be a superstructure to -Ga2O3. The superstructure parameters are found to vary both along the axis of the crystal and radially, which is due to variations in Ga : Sc ratio. A structural model of the Ga1.5Sc0.5O3 crystal is proposed. 相似文献
17.
Single phase -Fe4N type (Fe1–xNix)4N compounds (0 x 0.6 have been synthesized for the first time by controlled heat treatment of iron-nickel oxalates in a gaseous flow of NH3 xand H2. The preparation processes were investigated using differential scanning calorimetry (DSC), X-ray diffraction and Mössbauer spectroscopy. The results confirmed that annealing of oxalates in the NH3 and H2 atmosphere included the processes of dehydration, decomposition and reduction, nitrogenation and thermal decomposition of the nitrides. The decomposition and reduction occur simultaneously. The final products depend on the flow rate ratio of NH3 H2 and the annealing temperature. The formation conditions for the single phase -Fe4N type (Fe1–xNix)4N compounds are related to the nickel concentration, with increasing nickel content, the nitrogenation temperature decreased, in contrast the flow rate ratio of NH3 H2 increased. 相似文献
18.
Journal of Superconductivity and Novel Magnetism - We have investigated the electrical and magnetic properties of the compounds LaPt2As, LaPt2As2, and BaPt2As2 prepared by conventional solid-state... 相似文献
19.
Metastability of the K2NiF4 type aluminate LaCaAlO4 and its chromium diluted solid solution LaCaCr
x
Al1–x
O4 (x0.10) was evidenced at 1400C in air, in terms of demixing into the parent structures of the 11 intergrowth, i.e. the perovskite and rocksalt type LaAlO3 (LaCr
x
Al1–x
O3) and CaO, respectively. This behaviour is discussed comparatively with YCaAlCO4 and LaSrAlO4 whose structures are stable under the same thermodynamic conditions. The results of a structure analysis are used to emphasize the role of the nine-fold co-ordination of the (A
3+=Y3+, La3+; A2+=Ca2+, Sr2+) cations as mixing the twelve-fold co-ordination of A
3+ in A
3+AlO3 perovskite and the six-fold one of A
2+ in A
2+O rocksalt. Calcium-oxygen underbonding in the (La, Ca)-O-Al bridge is assumed to trigger the metastability of the intergrowth structure at high temperature. 相似文献
20.
I. V. Bodnar' 《Inorganic Materials》2002,38(7):647-651
CuAlS2, CuAlSe2, and CuAlS2x
Se2(1 – x) (0 < x < 1) single crystals were grown by chemical vapor transport in a close-spaced geometry and characterized by x-ray diffraction and differential thermal analysis. The results were used to map out the CuAlSe2–CuAlS2 phase diagram. The density of the crystals was found to vary linearly with x, while microhardness shows a maximum. The transmission and reflection data obtained near the intrinsic edge were used to determine the band gap E
g of CuAlS2, CuAlSe2, and the solid solutions. E
g was found to vary nonlinearly with composition. 相似文献