共查询到20条相似文献,搜索用时 31 毫秒
1.
《Solid State Communications》1987,63(11):961-964
Superconductivity transition has been observed by electrical resistance and a.c. magnetic susceptibility measurements in ErBaCuO and YbBaCuO systems. The highest Tc(ϱ=0) is 90.3K for ErBaCuO and 91K for YbBaCuO. 相似文献
2.
《Physics letters. A》1988,130(1):39-42
A TlBaCaCuO4.5+x compound has been investigated from the point of view of superconductivity. Depending on the heat treatment, one part of the samples exhibits superconductivity with an onset of 121 K and a zero resistivity of 106 K, while the other part of them shows only a sharp drop in resistivity at 130 K which hints at the existence of superconducting domains. This picture was confirmed by magnetic and ESR measurements giving possibility for estimation of the critical magnetic fields. 相似文献
3.
4.
《Physics letters. A》1987,126(1):55-57
A small amount of Pd addition increases Tc for the YBa2Cu3O7−y oxide. The maximum offset, midpoint and onset temperatures of the YBa2(Cu0.999Pd0.001)3O7−y oxide are 92.1, 95.0 and 105 K, respectively. Excess addition of Pd decreases Tc. The Tc change is consistent with the results of the lattice constants. 相似文献
5.
6.
《Solid State Communications》1987,63(7):641-643
We added small amount of Sc (0.05–0.35at.%) to BaYCu oxide and found that the superconductivity deteriorated drastically when the Sc content reached 0.325at.%. X-ray and electron diffraction showed that the orthorhombic perovskite structure changed to multi-phase structure with unidentified phases. The microstructures observed by TEM are of needle like morphology. Their phases are not yet identified. 相似文献
7.
《Solid State Communications》1987,64(3):325-326
Fluorine ions with an energy of 180keV at a dose of 1×1015 ions/cm2 have been implanted into YBa2Cu3Ox. After annealed at 800°C, the resistance of the new Y-Ba-Cu-F-O compound drops to zero at 148.5K. 相似文献
8.
《Solid State Communications》1987,63(5):389-393
Electron microscopy and electron diffraction have been applied to show that the orthorhombic phase in the compound Ba2YCu3O7−δ is responsible for the high superconducting transition temperature. A positive correlation is found between the volume fration of the orthorhombic phase and the superconducting transition temperature. By means of an “in-situ” heating experiment it is found that the orthorhombic phase is formed on cooling from a high temperature tetragonal phase with disordered vacancies. It is suggested that the low temperature tetragonal phase that occurs in the same specimens as the orthorhombic phase also contains an ordered arrangement of vacancies different from that present in the orthorhombic phase. The order-disorder transition associated with the structural vacancies is shown to be reversible, provided there has been no oxygen loss. 相似文献
9.
《Solid State Ionics》1988,31(2):127-130
Amorphous products were obtained in the LiBSe ternary system by quenching melts of Li2Se, B and Se mixture prepared at 100°C in sealed silica tubes. The vitreous region was slightly lower selenium composition than that of the Li2SeB2Se3 tie-line. The amorphous products were lithium ionic conductors and most of them showed contributions to their total conductivity. The amorphous product of composition Li25B36Se39 has the least electronic contribution to its total conductivity of 6.0 × 10−6 S/cm at room temperature. A new crystalline compound and crystalline LiBH4 were also obtained in LiBSe ternary. Both of them were lithium ionic conductors having conductivities of about 1 × 10−6 S/cm at room temperature. 相似文献
10.
11.
《Physics letters. A》2002,303(1):87-90
Superconductivity of rapidly quenched ribbons Ti53Zr27Ni20 at 1.94 K and the beginning of the transition to the superconductivity in ribbons Ti45Zr38Ni17 below 1.5 K were found. X-rays diffractometry measurements showed that the icosahedral quasicrystal phase is dominant in all samples. 相似文献
12.
13.
《Solid State Communications》1987,62(2):85-87
Superconductivity of the compounds of LaMCuO system with K2NiF4 type structure has been studied. For the sintered compounds with MBa, Sr and Ca, the highest onset transition temperatures, Tci, estimated from resistivity measurement are about 36.9K, 43.0K and 23.5K, respectively and the highest temperatures where the resistivity vanishes, Tcf, are about 27.8K, 34.0K and 15.5K, respectively. Almost complete Meissner effect has been confirmed by low frequency ac susceptibility measurement. Crystals of the compounds with MBa and Sr have been prepared. As the result of the preliminary experiment for a crystal with Ba, it is found that Tcf of the crystal is higher than any one of the sintered specimens with MBa, while the Tci of the crystal is nearly the same as the highest one of the sintered specimens. 相似文献
14.
《Physics letters. A》1998,244(5):449-453
A blue photoluminescence band centered at 440 nm was observed from SiGeSiO2 co-sputtered films at room temperature. This band gains intensity after the film was annealed at a temperature around 900°C in N2 atmosphere. From analysis of photoluminescence excitation, Raman and X-ray photoelectron spectra, it turns out that the luminescence is probably from some interfacial state between Si1−xGex nanoparticles and the SiO2 matrix. 相似文献
15.
《Solid State Communications》1996,100(10):727-730
The lattice dynamics and specific heat at constant volume for AlCu alloy system is studied using our previous treatment based on the microscopic electronic theory. Considering the volume and electron density effect on the dynamical matrix of the pure constituent, we obtain the band and local mode frequencies at the temperature-dependent specific heat in the Al1−x Cux solid solution. Then, using the data about the mean elastic wave and the specific heat extrapolated to the absolute zero temperature, the Debye temperature is presented for the Al1−xCux, Al1−xSix and Al1−xGex alloy systems. The Debye temperature decreases as a function of the Cu atomic fraction x for Al1−xCux alloy, and remarkably for Al1−xSix and Al1−xGex solid solutions. 相似文献
16.
《Surface science》1986,177(1):L887-L895
17.
《Physics letters. A》1987,123(1):34-36
The superconducting transition temperatures of a family of YBaCu oxides have been explored by dc resistivity measurements. Substitutions of magnetic and non-magnetic ions on Y, Ba and Cu sites are reported. For some compositions, achieving high superconducting transition temperatures is strongly dependent on growth conditions for the material. 相似文献
18.
《Solid State Communications》1987,64(2):217-226
Superconductivity around 90K is observed in mixed and single phase system of LnBaCuO (Ln = Y, Ho, Er). Resistivity, X-ray powder diffraction and AC susceptibility measurements were carried out on samples of the mixed phase systems Ln2−xBaxCuO4−y (Ln = Ho, Er), Y1.2Ba0.8Cu1+xO4+x−y(0<x<5) and single phase system Ba2LnCu3O7 (Ln = Y, Ho, Er). Ln2−xBaxCuO4−y consists of Ba2LnCu3O7, BaCuLn2O5, Cu2Ln2O5 and starting materials and shows a small diamagnetic signal below Tc in the temperature dependent AC susceptibility. Y1.2Ba0.8Cu1+xO4+x−y is a mixture of Ba2YCu3O7, BaCuY2O5 and CuO and also indicates a small diamagnetic signal at 92K. Interesting resistivity anomalies occur in the Y1.2Ba0.8Cu4O7−y and Ho0.8Ba1.2CuO4−y composites including large drops in the resistivity at ∼220 and ∼120K, respectively. The pure compounds, Ba2LnCu3O7 (Ln = Y, Ho, Er) show sharp resistive superconducting transitions and bulk Meissner effects of 90%. 相似文献
19.
《Physics letters. A》1987,123(1):31-33
We present the results of a study of the crystalline structure of the high-temperature superconducting (above 110K) phase in the single-phase ceramic compounds YBaCuO. We have concluded that the crystal symmetry of this HTS phase with chemical composition Y1.2Ba0.8CuO4−δ is orthorhombic type with crystallographic lattice constants a=0.3815 nm, b=0.3457 nm, c=2.650 nm. 相似文献
20.
《Journal of magnetism and magnetic materials》1987,67(1):20-28
We present an analysis of the magnetization process of NdFeB-type magnets which exhibit a constriction or a shoulder of the demagnetization curve near the remanence point Br. This constriction which drastically reduces the maximum energy product of the permanent magnet is discussed in terms of i) a siperposition of a soft and a hard magnetic phase, ii) an oxidation process of surface layers, iii) and the spin reorientation which changes the magnetic structure from easy c-axis to easy cone below 135 K. We demonstrate that the effect of surface oxidation and of a soft magnetic phase are of considerable influence over the entire temperature range while the influence of the spin reorientation is dominant below 150 K. The appearance of the cone structure prevents the application of NdFeB magnets in a magnetic circuit below 150 K. 相似文献