Zhou Guien

Zero resistance at 132K in the multiphase system of Bi1.9−xPbxSb0.1Sr2Ca2Cu3Oy with x=0.3, 0.4

Abstract Superconducting properties of the multiphase compounds of ( Bi 1.9− x Pb x Sb 0.1) Sr 2 Ca 2 Cu 3 O y have been investigated. Zero resistance at 132K has been observed with x =0.3 and 0.4. Two samples with 132K zero resistance were stable in low temperature circling (77K to 200K). Zero resistance were down to 112K( x =0.3) and 106K( x =0.4), but the a.c susceptibilities of the two samples still have large drop at 132K after several circles from 77K to room temperature.

Growth of Bi2Sr2CaCu2O8 single crystals from Bi-rich melts

Abstract High-quality Bi 2 Sr 2 CaCu 2 O 8 single crystals with dimensions up to 15x4x0.05 mm 3 were grown from the starting composition Bi 2+ x Sr 2 CaCu 2 O y , where x =0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6 and 0.7. Different amounts of Bi 2 O 3 in excess are included in each crystal growth run to act as flux for the growth and the optimum concentrations of the flux amount have been found. Structure characterization of a high-quality 2212 free crystal of 5x1.8x0.02 mm 3 was conducted by the (00 l ), ( h 00) and (0 k 0) X-ray diffractions, using a rotating anode diffractometer, and the back-reflection Laue photograph. It is found that melting incongruency is the main problem encountered in the growth of large and pure-phase single crystals from Bi 2 O 3 -rich melts and we have shown that, for x =0.8, crystals of 2212 phase and crystals of 2201 phase coexisting with CuO are obtained from the two segregated parts of the Bi-rich melts.

The superconducting properties in Bi2−xSbxSr2Ca2Cu3Oy compounds (x=0.05, 0.1, 0.15, 0.2)

Abstract Superconducting properties of a new series Bi 2−x Sb x Sr 2 Ca 2 Cu 3 O y ( x =0.05, 0.1, 0.15, 0.2) have been reported in this paper. All of these samples have two superconducting transitions. The first superconducting transition is at about 120 K, zero resistance temperature is about 75 K. A new high- T c phase appears because of the substitution of Sb in the Bi-Sr-Ca-Cu-O system

THE SYNTHESIS AND SUPERCONDUCTIVITY OF A NEW-TYPE OF BI-1212 PHASE (BI, CD)SR2(Y, CA)CU2OZ

Abstract A novel series of Bi-1212 superconducting cuprates (Bi 1- x Cd x )Sr 2 (Y 1- y Ca y )Cu 2 O z has been discovered in this work. The structure was suggested to be that of (Bi, Cu)Sr 2 YCu 2 O z with Cd 2+ ions substituting into the Cu 2+ sites in the rock-salt-type (Bi, Cu)O layers. The superconductivity was induced in the as-prepared samples by treatment under oxygen pressure of 10 atm at 800°C with a composition of (Bi 0.27 Cd 0.73 )Sr 2 (Y 0.7 Ca 0.3 )Cu 2 O z . The zero-resistivity temperature is 26 K.

Phase identification of 140 K superconducting Bi2Sr2Ca2Cu3O10-δ doped with Sb and Pb

The Tc=140 K superconductor Bi2Sr2Ca2Cu3O10- delta doped with Sb and Pb was characterised by powder X-ray diffraction, electron diffraction and electron probe microanalysis. It was observed in the specimen that there was a new phase Bi3Sb0.8Pb0.2Sr4.1Ca3.9CuO15+ delta besides 2212, 2223 and a little CuO. The new phase belongs to the monoclinic system with cell dimensions a=22.14, b=5.902, c=19.91 AA and beta =99.7 degrees .

SUPERCONDUCTIVITY AT 27-K IN NB-1222 CUPRATE - NBSR2(GDCE)2CU2OY

Samples of NbSr2Gd2-xCexCu2Oy have been prepared by solid state reaction. The X-ray powder diffraction patterns show that a single phase can be formed in the composition range of 0.49 < x< 0.51 that has the TaSr2 (NdCe)2Cu2Oy Structure [ 11, the cell para

Observation of the modulated structure in Bi2Sr2CaCu2Oy single crystals by using an X-ray rotating-anode diffractometer

Abstract With a conventional X-ray rotating-anode diffractometer, structure characterization of a pure and highly oriented Bi 2 Sr 2 CaCu 2 O y single crystal sheet with large dimensions of 5×1.8×0.03 mm 3 has been conducted. Incommensurate satellites corresponding to a modulation 0.21 b ∗ + c ∗ have been observed up to second order. Apart from the asymmetry in intensities of the symmetrically located satellites, we revealed one more characteristic of the modulated structure, that the satellites are stretched along the c ∗ direction to form poles in reciprocal space. The technique used is suggested to be convenient and practical for studies concerning especially the modulations for large crystals.

Preparation and characterization of ultrafine powders of the yAg-Cu Alloys by γ-radiation method

Abstract Ultrafine powder of the Ag-Cu alloy with average particle size or 25 nm has been prepared successfully by the γ-radiation method from the solution containing Ag(NH3)42+ complex ions. The copper content in the Ag-Cu alloy is 9.44 wt.%. The method can be processed under ambient pressure at room temperature.

Structural Characteristics of 2212-Phase Single Crystal in the Bi-Sr-Ca-Cu-O Superconductor

A single crystal of Bi-Sr-Ca-Cu-O 2212 superconducting phase has been studied by combining the Laue method with the method of X-ray diffractometry. It is suggested that the single-crystal structure of a superconductor is a modulated structure of a three-dimensional period coexisting with a two-dimensional lattice. In the structure, the Bi-concentrated bands, which form a three-dimensional modulated structure that corresponds to the results observed in high-resolution electron microscopy, do not entirely enter the parent structure lattice, but divide the parent structure into oxygen-deficient pervoskitelike layers. The pervoskitelike layer has a quasi-two-dimensional structure. The element modulation of Sr and Ca appears in the two-dimensional lattice, which is caused by the effect of Bi-concentrated bands. Meanwhile, the superlattice is formed on the ab plane. The three-dimensional structure of periodic modulation is formed by the pervoskitelike layer and Bi-concentrated band as a unit.

The effect of cation disorder on electrical transport properties of Nd0:7(Ca, Sr, Ba)0:3MnO3

The electrical transport properties of a series of samples, Nd0.7(Ca,Sr,Ba)0.3MnO3, with a fixed average A-site cation radius rA have been studied. Infrared spectra revealed that the symmetry of the local MnO6 octahedra reduces due to the size differences between various A-site ions. From the metal transition temperature Tm up to room temperature, the variable-range-hopping conduction mechanism has been observed, and Tm exhibits a systematic decrease with increasing A-site cation disorder. In the very-low-temperature range, we have observed that resistivity increases with decreasing temperature.