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The XPS(X-ray photoelectron spectroscope) measurements of the 80K phase Bi-Sr-Ca-Cu-Li-O ceramics were carried out on surfaces obtained by polishing in ultrahigh vacuum. The results show that the chemical bond natures of Bi and Sr almost did not change, but the binding energies of Ca, Cu and O shifted apparently toward higher energy when Li doped in the Bi-Sr-Ca-Cu-O system. The XPS spectrum of O Is has only singe peak (528.8eV) from clean surfaces polished in vacuum and consists of the OH (531eV) and OL (528.8eV) components from conventionally polished surfaces.

XPS measurements have been carried out to study the difference in the electronic state between the pure 2212 single crystal and the Gd-doped 2212 single crystal in Bi-based system. Experimental results show that the suppression of superconductivity by Gd doping is caused by the hole filling in the O2p orbital. The problems, such as that about the ratio of the intensity of the satellite peaks to that of main peak (Is/Im) the physical property of Bi-O layer and the contribution to the density of state (DOS) at Er for the Bi-based 2212 phase have also been discussed.

Samples with nominal composition Bi2-xPbxSr2Ca2Cu3Oy(x = 0.30;0.35;0.40;0.45) have been prepared by solid state reaction. Phase and structure analyses have been performed, and the resistance-temperature relation and dc susceptibility have also been measured. The results show that the sample with x = 0.35 is a single-phase material. X-ray analysis and electron differaction indicate that its phase structure is similar to that of 2223 phase, it is tetragonal with a = b = 5.414?, c = 37.106?, we observed also the modulated structure along a and b. The results of resistance-temperature and dc susceptibility measurement show that, when T = 50 K, there is only one superconducting phase of 107K. In addition, we find that the preparation condition of the single-phase material (composition, sintering temperature and the quenching rate) is stringent. Like the 1-2-3 phase material, the oxygen content not only influences the phase, zero-resistance temperature of the sample, but also influences the transport property of normal state.

A series of samples with different nominal composition have been prepared and their structure, resistivity and a.c. magnetic susceptibility have been investigated. Zero resistance temperature T ce as high as 110.5K and 101K have been reached in the nominal composition Bi 3 Sr 2 Ca 2 Cu 3 O y and Bi 2 Sr 2 Ca 2 Cu 3 O y samples, respectively. A basically single high-T c phase with the nominal composition Bi 2 Sr 2 Ca 6 Cu 7 O y has been obtained. It is suggested that the samples' T ce is chiefly depended upon the grains boundaries.

Two kinds of single crystal YbBa2Cu3O7-y and ErBa2Cu3O7-y have been grown by the fluxed method. They are orthorhombic structure with space group Pmmm, cell parameters are a=3.88A, b=3.82A, c=11.68A and their typical size are 3×2×2mm3. The superconducting critical temperature is over 90K. Their superconductivity is discussed.

The R(H) and Jc(T) of single phase material Bi3PbCa3Sr3Cu4Oy were investigated. As the temperature belows 65K, the sample likely shows the characteristics of homogeneous superconductors. Very high critical current density and no negative magnetoresistance are observed. This distinct property distinguishes the new material from other ceramic superconductors.

Results of resistivity, a.c. magnetic susceptibility, Hall effect and superconductivity for single phase Ba 2 YCu 3 O 7− δ are reported. The positive value of Hall constant above T c indicates that the carriers of the sample are hole-like in normal state and its concentration is about 1.1×10 21 cm -3 at room temperature. A large anomaly of R H near T c is observed which may be indicative of granular superconductivity or be related to the intrinsic quality of this class of oxides.

A series of (YBa 2 Cu 3 O 7−y ) 1−x Ag x samples were prepared using solid state reaction method. On the basis of X-ray diffraction analysis, scanning electron microscopic observation, measurements of the resistivity; a.c. magnetic susceptibility as well as the critical current density, we find that enhancing the intergranular coupling by improving the properties of grainboundaries, while the properties of grains are kept unchanged, helps to increase the critical current density. The dependences of the critical current density on the Ag content, the temperature and the magnetic field are discussed. Our results suggest that eliminating grainboundaries together with improving the properties of grains may be an effective way in raising the critical current density in bulk materials.

During the preparation of Ba-Y-Cu-O superconductors, a new crystal having a super-K 2 NiF 4 structure was found. Single crystals of the new phase Ba x Y 2− x CuO 4 have been obtained. The cell parameters are a = 10.290 A, b = 5.692 A an d c = 13.187 A. The dimension of the crystal is 3.5×1×1 mm 3 .

By measuring the structure, superconductivity, magnetoresistance of polycrystalline single-phase YBa2Cu3O7-δ samples, the phenomena of negative magnetoresistance and the hysteresis of the magnetoresistance have been studied. An analysis of the origin of the influence of grain boundaries on the superconductivity and the electronic transport properties are given.

Results of resistivity, ac magnetic susceptibility, and Hall-effect measurements for Ba1.2Y0.9V0.9Cu3O7-δ are reported. The positive value of Hall constant indicates that the material conducts via hole with a carrier concentration of 1.6×1021cm-3 at room temperature. A large anomaly in RH near Tc is observed.

The measurements of X-ray diffraction, dependence of d.c. resistance on temperature and Hall effect have been performed for YBa2Cu3−xZnxOy system. The doped samples in 1-2-3 phase all exhibit metallic behavior and the hole carrier concentration experiences a nonmonotonous variation, but still larger than that of the perfect sample. The picture of localization is applied to explain these phenomena. The TC suppression mechanism has been discussed for this system.

The Raman spectra of a set of samples with nominal composition Ba x Y 1−x CuO 3 (0.005 ⩽ x ⩽ 0.8) which are synthesized under the same condition have been measured. It is observed that the main characters of Raman spectrum are quite different for the two groups of samples with Ba concentration being 0.3 ⩽ x ⩽ 0.8 and 0.005 ⩽ x ⩽ 0.075 respectively. It just coincides with the results two types of phase structures and the difference in superconductivity related to the two ranges of composition. Based on a comprehensive analysis of the results above, the authors suggest that the Raman peak near 605cm -1 likely corresponds to the vibration of CuO 6 octahedra breathing-mode, which play an important role in this system for achieving high transition temperature.

Superconductivity transition has been observed by electrical resistance and a.c. magnetic susceptibility measurements in ErBaCuO and YbBaCuO systems. The highest T c ( ϱ =0) is 90.3K for ErBaCuO and 91K for YbBaCuO.

To explore high Tce in Bi-Sr-Ca-Cu-O system, many different nominal compositions have been investigated. Zero resistance temperature Tce as high as 105K and only one sharp superconducting transition in a.c. susceptibility measurement has been observed in the nominal composition Bi2Sr2Ca3Cu4Oy by using the method of crystallization from glassy Bi-Sr-Ca-Cu-O at 875° C for above 50h.

We report the structure and superconductivity of single crystal YBa2Cu3O7−δ. The maximum dimensions of single crystal are 2.5×2.5×1.5 mm3. It is orthorhombic structure with space group Pmmm, cell parameters are a =3.88 A , b =3.82 A , c =11.68 A . The superconducting critical temperature is Tc=91 K. And a resistance anomalous phenomenon is also observed at 280 K.

A new hexagonal crystal Ba 4 Pt 1+ x Cu 2− x O 9− y was grown from the Ba-Y-Cu-O system in a K 2 CO 3 flux. Weissenberg photographs proved that the sample is a single crystal. Electron diffraction patterns clearly show the hexagonal symmetry. X-ray powder patterns give the exact cell constants, a = 5.803 A and c = 8.450 A.

In this paper, two main phases are found in the Bi2-xPbxCa2Sr2Cu3Oy system One is 4334 phase, another is a new one with cell parameters a =5.09 A , b =5.18 A , and c =36.98 A . The results of ac susceptibility measurements in the Bi2-xPbxCa2Sr2Cu3Oy system there are three superconducting transition at 110K, 95–100K and 65K respectively. As the x is increased from 0.1 to 1.2, the zero resistance temperature (Tce) is raised to 107K (x=0.3-0.5) at first, then is reduced to 64K gradually.

The structure and compositions of phases in the superconducting Y(Yb)-Ba-Cu-O systems with three nominal compositions have been investigated in a transmission microscope (TEM). Based on our improved quantitative microanalysis method, more accurate contents of Y, Yb, Ba and Cu in phases have been obtained simultaneously with the structure determination by electron diffraction. There is no Ba in Y 2 Cu 2 O 5 phase and a little amount of Ba in (Y, Yb) 2 Cu 2 O 5 phase. The more Y 1 Ba 2 Cu 3 O 7 , the better the superconducting property.

The ac magnetic susceptibility, the magnetoresistance R(H) and the dependence of the resistivity on temperature under different applied field were investigated in the Pb-doped Bi-Ca-Sr-Cu-O system. A superconducting phase with Tc similar 100K exists in this sintered sample. It forms a well connecting network, and therefore the Josephson coupling between the superconducting grains is sharply improved by doping lead.

In this letter, we report that superconducting Bi-Ca-Sr-Cu-O single crystals with the typical size 2×2×1 mm3 were grown with the flux methed successfully. The single crystal structure is proved by Laue photograph. Weissenberg photograph shows that it belongs to orthorhombic system with cell constants: a=5.42 A , b=27.18 A , c=30.67 A . The superconducting transition temperatures are Tc(mid)=83 K, Tce=79 K. A.C. magnetic susceptibility measurement shows the crystal has strong diamagnetic. The relation between superconductivity and the structure is discussed.

In the (Bi,Pb)CaSrBaCuO system, a rather large orthorhombic cell with a=5.4A, b=26.9A and c=30.7A have been found. The ac susceptibility measurement shows that there exists only one superconducting transition at 110K, the zero-resistance temperature is as high as 106K.

A new superconducting oxide GdxBa1−xCuO3−y with Tc (ρ=0) above 92K has been successfully synthesized by the ceramic technology. The samples with composition of x=0.5, 0.625 and 0.9 are all observed with high Tc superconductivity. The highest Tc for samples measured is observed in Gd0.5Ba0.5CuO3−y which has a resistive midpoint of 95K with a width of 1.5K, and a zero-resistance temperature of 92.5K. The results of a.c. magnetic susceptibility measurement are also reported.

The electrical resistivity and the thermopower are measured on the single phase superconductor Ba2YCu3O9-δ (δ=2.1). The results indicate that the temperature dependences of the resistance and thermopower exhibit typical metallic behaviour, and the sample conducts via electrons at high temperatures. The behaviour of the thermopower can be described with Mott's semi-classical model. The specific heat of electrons in normal state has been estimated 780mJ/K·mole at 200K, i.e. γ=3.9mJ/K2·mole. Unusual phonon-drag effect is observed above the superconducting transition temperature Tc. Below Tc, the electrical resistivity and the thermopower all drop to zero corresponding to a superconducting ground state.

The crystal structure, electron transport properties in normal state and superconductivity of a series of YBa2Cu3−xNixO7−y samples (0≤×≤0.5) were investigated. With the increase of the Ni content, the resistivity in normal state increased, and the resistance-temperature coefficient changed from metallic type to semiconductive type. The intimate correlation among the superconductive critical temperature, crystal structure and resistivity, espically the correlation of Tc∼ P strongly suggested that the localization effect of the electrons be an important factor to the decrease of Tc.

With the aim of preparing a single high-Tc phase in the BiPbSrCaCuO system, optimization of the composition and heat treatment have been studied. It has been found that the temperature range at which the high-Tc phase forms is very narrow (850–880°C). The high-Tc single phase Bi2.5Pb0.5Sr2Ca2Cu3Oy has been prepared. The zero-resistance temperature (Tce) is as high as 105K. There are no steps in the resistivity and the susceptibility. The structure is tetragonal with a=5.414 A and c=37.106 A . It is suggested that the phase with c=37.106 A is responsible for the high temperature (110K) superconductor.

The temperature dependence of the Hall coefficient between 50 and 250K is measured by a standard technique in single phase Bi3PbCa3Sr3Cu4Oy. The relation n (T)=n0(1+aT) is well satisfied in the normal state. The carrier density n is about 3.09×1021cm−3 at 250K. The positive value of the Hall coefficient indicates that the material dominately conducts via holes. A large anomaly of RH is observed between 113 and 90K, this anomaly is associated with the microstructure of sample and analysed in terms of a simple model.

In this paper, a series results in single crystal GdBa2Cu3O7−y, which include anisotropic behavior of resistivity in normal state and superconducting transition temperature, have been reported. The authors find that both ϱ‖ (‖ ab plane) and ϱ⊥ (⊥ab plane) are fitted very well to the Anderson-Zou relationship: ϱ = A T + BT . The superconductivity in c axis is weaker than that in ab plane: Tce⊥ is 2K lower than Tce‖. When the applied magnetic field H is parallel to the ab plane the signal of the A.C. magnetic shielding is 82% of that when H is perpendicular to the ab plane.

To explore high Tc in Bi-Sr-Ca-Cu-O system, many different nominal compositions have been prepared by using the traditional solid state reactions and using the method of crystallizion from glass samples. The better results are as follows: single high-Tc phase and essentially single high-Tc phase have been obtained from Bi1.8Pb0.35Sr2Ca2Cu3O and Bi2Sr2Ca6Cu7O respectively, by solid reaction. Basically single hign-T phase material with nominal composition Bi2Sr2Ca3Cu4Oy has been produced by the method of crystallizion from glass samples. The relationship between the starting composition heat treatment, preparation methods and high Tce is briefly discussed.