Jingkui Liang

THE SUPERCONDUCTIVE PROPERTIES AND CRYSTAL-STRUCTURE OF BA2(Y1-XPRX)CU3O9-Y SOLID-SOLUTIONS

A series of Ba2(Y1−xPrx)Cu3O9−y solid solutions were prepared with the orthorhombic distorted perovskite structure. The compound Ba2PrCu3O9−y belonging to tetragonal system is a good semiconductor. The superconductivity is observed for samples withx<0.6. With the increase of Y content, the distortion of crystal structure is greater and the superconductive transition temperature of zero resistanceTc(0) raises.

Crystal structure and superconductivity of TlBa2CaCu2O6.5

AbstractIn this article, the crystal structure and superconductivity of a new superconducting phase TlBa2CaCu2O6.5 (Tc=72.5 K) in Tl−Ba−Ca−Cu−O system are studied. The crystal structure of the compound TlBa2CaCu2O6.5 has been determined by means of X-ray powder diffraction method. It belongs to primary tetragonal lattice with lattice parameters:a=3.847 Å,c=12.73 Å. Its space group isD4h1−P4/mmm. Each unit cell contains one formular unit. The arrangements of ions in a unit cell are following:1 Ca, and 1 Tl cations occupy 1(a) and 1(d) equivalent point positions respectively.2 Cu cations occupy 2(h) (z=0.127) equivalent point positions.2 Ba cations occupy 2(g) (z=0.281) equivalent point positions.6.5 O anions respectively occupy 1(b), 2(h) (z=0.281) and 4(i) (z=0.127) equivalent point positions. Occupation factor is 0.929. The crystal structure of TlBa2CaCu2O6.5 is quite similar to those of the other superconducting phases in Tl−Ba−Ca−Cu−O system. All cations are distributed at positions of (0, 0,z) and (1/2, 1/2,z) alternately. The oxygen deficient pseudo-perovskite unit Ba−Cu−Ca−Cu−Ba is separated two Tl−O layers in the crystal structure of Tl2Ba2CaCu2O8. However, the oxygen deficient pseudo-perovskite unit Ba−Cu−Ca−Cu−Ba is separated by single Tl−O layer in the crystal structure of TlBa2CaCu2O6.5. The relations among the crystal structures of the superconducting phases as well as the relation between the crystal structure and superconductivity are discussed.

Thermodynamic treatment of the Nd2O3CuO binary system

Abstract The Nd2O3CuO phase diagram was calculated by using a regular solution model. The interaction parameters were derived from reliable experimental data. The phase diagram was constructed after an approximate treatment of the decomposition of CuO at 1025 °C. The calculated results were compared with experimental data.

Superconductivity and magnetic properties in Pr0.2Yb0.8−xLaxBa2Cu3O7−δ

The crystal structure, superconductivity and magnetic properties of the title compounds have been investigated. The results revealed that with the concentration of Pr being constant, the transition temperatureTc of this system decreases with the increasing of La, or rather with the increasing of effective ionic radii of rare earth elements and the superconductivity disappears at aboutx=0.6. The coefficient of electron specific heat and the density statesN (0) which were infered from the magnetic measurements also decrease with the increasing of the effective radii. The relation between the radii of rare earth elements and hybridization is briefly discussed.

thermodynamic calculation of atmospheric pressure and high pressure (P = 2500 atm) phase diagram of LiIO3-NaIO3 binary system

Based on the advanced thermodynamic models, the optimized thermodynamic data for these two systems were derived from experimental phase dragrams. In optimization the excess molar volume of liquid was represented by a polynomial of composition and optimized by the combination of the two experimental phase diagrams. The calculated and experimental phase diagrams were in good agreement. This indicated the present method for treatment of excess molar volume is reasonable. The calculated results showed that the application of pressure on the present system restrains the formation of short range order of atoms in the liquid at about x = 0.85mol NaIO3.

The Crystal Structure and Superconductivity of the Superconducting Phase TISr2 (Ca, La)1 Cu2O7

The crystal structure and superconductivity of the new superconducting phase TISr2(Ca, La)1Cu2O7 in the TlSrCaLaCuO system are investigated. The zero resistance superconducting transition temperature Tc(0) 71 is 76, 43, and 28 K for samples with the nominal composition TI2Sr2Ca2 Lax, Cu3O10+1.5x with x = 0.5, 1.0, 1.5, and 2.0, respectively. The crystal structure of the superconducting phase TlSr2(Ca, La)1Cu2O7 is determined by means of X-ray powder diffraction method. It belongs to the primary tetragonal system with the space group D - P4/mmm. Its lattice constants are a = 0.3800 nm and c = 1.1960 to 1.2042 nm (depending on the La content in nominal composition of samples). Each unit cell contains one formula unit. The positions of the ions in unit cell are as following: 1(Ca, La) disorderly occupy 1(d) equivalent point position; 1 Tl cation occupies 1 (a) equivalent point position; 2 Cu cations occupy 2(g) equivalent point position with z = 0.365; 2 Sr cations occupy 2(h) equivalent point position with z = 0.210; 7 0 anions occupy 1 (c), 2(g) (z= 0.165) and 4(i) (z = 0.365) equivalent point positions. It is found that the similarity of the cation-oxygen coordination polyhedron plays a more important role for the substitution of the cations in the superconducting phase with oxygen-deficient pseudoperovskite structure. Die Kristallstruktur und Supraleitfahigkeit einer neuen supraleitenden Phase TlSr2(Ca, La)1Cu2O7 im TlSrCaLaCuOSystem wird untersucht. Die Nullwiderstands-Supraleitungsubergangs temperatur Tc(O) betragt 71, 76, 43 und 28 K fur Proben mit der nominellen Zusammensetzung Tl2Sr2Ca2LaxCu3O10+1,5x mit x= 0,5, 1,0, 1,5 bzw. 2,0. Die Kristallstruktur der supraleitenden Phase TlSr2(Ca, La)1Cu2O7 wird mittels Rontgenbeugung an Pulverproben bestimmt. Sie gehort zum primaren tetragonalen System mit der Raumgruppe D - P4/mmm. Ihre Gitterkonstanten sind a = 0,3800 nm und c = 1,1960 bis 1,2042 nm (abhangig vom La-Gehalt bei Nominalzusammensetzung der Proben). Jede Einheitszelle enthalt eine Formeleinheit. Die Lagen der Ionen in der Einheitszelle sind folgende: 1(Ca, La) besetzen fehlgeordnet 1(d) aquivalente Punktlagen. 1 Tl-Kation besetz 1(a) aquivalente Punktlagen. 2 Cu-Kationen besetzen 2(g) aquivalente Punktlagen mit z = 0,365. 2 Sr-Kationen besetzen 2(h) aquivalente Punktlagen mit z = 0,210. 7 0-Anionen besetzen 1(c), 2(g) (z = 0,165) und 4(i) (z = 0,365) aquivalente Punktlagen. Es wird gefunden, das die Ahnlichkeit der Kationen-Sauerstoff-Koordinationspolyeder eine grosere Rolle fur die Substitution der Kationen in der supraleitenden Phase mit Sauerstoffunterschus-Pseudo Perovskitstruktur spielen.