Pan Guoqiang

Hall effect in single phase Ba2YCu3O7−δ

Abstract 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.

The Behaviour of Negative Magnetoresistance and Hysteresis in YBa2Cu3O7-δ

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.

In situ high temperature X-ray diffraction studies of ZnO thin film ∗

An epitaxial ZnO thin film was entirely fabricated by pulsed laser deposition. Both the orientation and the size of the crystallites were studied. The X-ray diffraction (XRD) patterns of the film show strong c-axis oriented crystal structure with preferred (002) orientation. The Phi-scan XRD pattern confirms that the epitaxial ZnO exhibits a single-domain wurtzite structure with hexagonal symmetry. In situ high-temperature XRD studies of ZnO thin film show that the crystallite size increases with increasing temperature, and (002) peaks shift systematically toward lower 2θ values due to the change of lattice parameters. The lattice parameters show linear increase in their values with increasing temperature.

High-Tc superconductivities and electronic structures of some (BaxY1−x)CuO3 species by x-ray photoelectron spectroscopy

Abstract The electronic structures of a set of species (BaxY1−x)CuO3 have been investigated by means of X-ray photoelectron spectroscopy. The mid-point transition temperature Tc correlated monotonically with the density of states at the Fermi level. Evidence was found for the existence of a low valence state of barium, Ba+2−σ in these ceramics, the ratio Ba+2−σ/ Ba+2 being very likely of great importance to the theoretical understanding of their superconductivity.

Hall effect in superconducting oxide Ba-Y-V-Cu-O

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.

Electronic structure of the diaquabis(hydrogen malato) copper(II) crystal

SummaryThe electronic absorption and e.s.r. spectra of a crystal of the title compound [Cu(H2O)2 (C4H5O5)2] were recorded and experimental results are discussed quantitatively, using ligand field theory and the radial wave function of bound CuII. The electronic structure of the compound is consistent with its crystal structure.

High Tc superconductivity in single crystal YBa2Cu3O7-δ

Abstract 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.

Zero resistance above 90K in superconducting oxides ErBaCuO and YbBaCuO

Abstract 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.

Strain Induced Metastable Phase and Phase Revolution in PbTiO3-CoFe2O4 Nanocomposite Film

An inter-component epitaxial strain-induced PbTiO3 metastable phase is observed in a PbTiO3-CoFe2O4 epitaxial composite film, corresponding to the dielectric anomaly reported previously. High-resolution synchrotron radiation X-ray diffraction and first principles calculation demonstrate the coexistence of different PbTiO3 phases, even a possible morphotropic phase boundary in the film, elucidating the underlying microscopic mechanism of the formation of PbTiO3 metastable phase. This sheds light on the design and manipulation of electromechanical properties of epitaxial films, through the strain engineering.

X-ray photoelectron spectroscopy study of the single phase high-Tc superconductor YBa2Cu3O9-δ

X-ray Photoelectron Spectroscopy (XPS) was employed to study the single phase high-Tc superconductor YBa2Cu3O9-δ. Comparison of the observed valence band spectrum with the theoretical spectrum of Mattheiss is given. The core level spectrum of Ba 3d5/2 was examined. The results of Y2Cu2O5 and Y2BaCuO5 are also reported.