Jk Liang

The crystal structure and superconductivity of new superconducting phase TlSr2Ca0.5Sm0.5Cu2O6.75

Abstract The crystal structure of superconducting phase TlSr2Ca0.5Sm0.5Cu2O6.75 with Tc(0) = 37.6K in Tl-Sr-Ca-Sm-Cu-O system has been determined by means of X-ray powder diffraction method. It belongs to primary tetragonal cell with a = 3.817, c = 12.054 A . Its space group is D14h-P4/mmm. Each unit cell contains one formula unit. The positions of ions in unit cell are as following: 0.5 Ca and 0.5 Sm cations disorderly occupy 1(d) equivalent point position. The occupation factor for each of them is 0.5. Tl cation occupies equivalent point position 1(a). 2 Cu cations occupy 2(g) with z = 0.365. 2 Sr cations occupy 2(h) with z = 0.210. 7 O anions respectively occupy 1(c), 2(g) (z = 0.165) and 4(i) (z = 0.365) equivalent point positions. The crystal structure of TlSr2Ca0.5Sm0.5Cu2O6.75 is very similar to that of TlBa2CaCu2O6.5 in Tl-Ba-Ca-Cu-O system or RBa2Cu3O7 in R-Ba-Ca-O system. In the superconducting phase with oxygen-deficient pseudo-perovskite structure, the similarity of cation-oxygen coordination polyhedron is important for the substitution among the cations.

Phase diagram of the BaOCuOY2O3 system and the relationship between composition and superconductivity

Abstract The phase diagram of the BaYCuO ternary system was determined. In the CuO-rich region, two compounds were obtained: Ba 2 YCu 3 O 9− y and Y 2 CuBaO 5 . Ba 2 YCu 2 O 9− y is a high T c superconductor ( T c ≈ 90 K). The relationship between composition and superconductivity was studied, and the most suitable technique for superconductor preparation was determined.

Synthesis and crystal structures of new bismuth oxychlorides

Abstract A new Sillen phase I: Bi 1.7 Ca 2.7 O 4− y Cl 4 with X1X3 structure has been prepared. It crystallizes in space group P4/mmm with lattice parameters a =3.876(1), c =16.83(1) A . Incorporation of (CuO 2 ) sheets results in a new layered compound II: Bi 2.4 Ca 3.1 CuO 6− y Cl 5 . It also assumes a tetragonal crystal structure with space group P4/mmm and cell dimensions a=3.863(3), c =19.85(1) A . Although phase II contains one (CuO 2 ) sheet that usually gives high-Tc superconductivity when the copper oxidation states are suitably adjusted, our trial to induce superconductivity by doping has been unsuccessful.

A new type of borate double salt: structure of LiBa2B5O10

Time-resolved infrared spectroscopy is used to study the coordinatively unsaturated species eta-5-C5H5)Mn(CO)x (x = 2 and 1) generated by 266- and 355-nm laser photolysis of (eta-5-C5H5)Mn(CO)3 in the gas phase. (eta-5-C5H5)Mn(CO) is the predominant photoproduct upon 266-nm photolysis while both (eta-5-C5H5)Mn(CO) and (eta-5-C3H5)Mn(CO)2 am produced upon 355-nm photolysis. IR spectra in the region of 1820-2033 cm-1 are assigned for the coordinatively unsaturated species (eta-5-C5H5)Mn(CO)x and found to be in major disagreement with those obtained in condensed phases. The rate constants for the reactions of (eta-5-C5H5)Mn(CO)2 and (eta-5-C5H5)Mn(CO) with CO are determined to be (5.9 +/- 0.4) x 10(11) and (6.7 +/- 0.2) x 10(12) cm3 mol-1 s-1, respectively. The rate constant for the reaction of (eta-5-C5H5)Mn(CO) with CO is on the order of 1/10 gas kinetic while the corresponding value for (eta-5-C5H5)Mn(CO)2 is over an order of magnitude smaller. The magnitudes of the rate constants for the reactions of (eta-5-C5H5)Mn(CO)x with CO are compared with those of (eta-6-C6H6)Cr(CO)x previously observed and are discussed in terms of the change of spin states of these reactions. In addition, it is found that the presence of care gas Q (Q = Ar, He, and Xe) has remarkable influence on the kinetic behavior of (eta-5-C5H5)Mn(CO)2, implying the formation of rare-gas complexes (eta-5-C5H5)Mn(CO)2.Q in the gas phase.

Composition and superconductivity in Bi-Sr-Ca-Cu-O and substituted systems

The composition of the superconducting phase Bi4(Sr3±xCa3∓x)Σ=6Cu4O16, has been determined by means of a sysmetic investigation of the relationship between composition and superconductivity, and phase analysis. The superconducting phase belongs to tetragonal system witha=0.3825 nm,c=3.082 nm, space group (S.G.) 14/mmm. The effect of strontium and calcium contents in the Bi(Sr1±xCa1∓x)Σ=2Cu2O5.5, system and substitution in the Bi1−xAxSrCaCu2O5 (A=V, Gd, Y) and BiSrCa1−xPbxCu2O5.05 systems on superconductivity, have been investigated. In the Bi-Sr-Ca-Cu-O system, there are two superconducting phases corresponding to transition temperatures of 110 and 80 K, respectively. The difference between the two superconducting phases may be due to the stacking difference of atoms along thec direction in the structure and their oxygen content.

The crystal structure and superconductivity of the new superconducting phase TlSr2Ca0.5Er0.5Cu2O6.75

AbstractThe crystal structure of the superconducting phase TlSr2Ca1−xErxCu2O6.5+x/2 (x=0.5) in the Tl−Sr−Ca−Er−Cu−O system was determined using the X-ray powder diffraction method. It belongs to a primary tetragonal cell with lattice constantsa=3.798,c=12.014 Å, with a space group ofD4h1−P4/mmm. Each unit cell contains one formula unit. The positions of ions in the unit cell are as follows:0.5 Ca and 0.5 Er cations disorderly occupy 1(d) equivalent point position, each with an occupation factor of 0.5;1.Tl cation occupies the equivalent point position 1 (a);2.Cu cations occupy 2 (g) withz=0.365;2Sr cations occupy 2(h) withz=0.220;7O anions respectively occupy 1(c), 2(g), (z=0.165) and 4(i) (z=0.365) equivalent point positions. The zero-resistance superconducting transition temperatureTc(0) decreased slightly with increased Er content in the Tl−Sr−Ca−Er−Cu−O system. The crystal structure of TlSr2Ca0.5Er0.5Cu2O6.75 is very similar to that of TlBa2CaCu2O6.5 in the Tl−Ba−Ca−Cu−O system or RBa2Cu3O7 in the R−Ba−Cu−O system. In the superconducting phase with an oxygen-deficient perovskite-like structure, the similarity of cation-oxygen coordination polyhedra is important for cation substitution.

Crystallization of BaxSr1-x(NO3)(2) solid solutions from aqueous solutions and the influence of Ba2+ ion on Sr(NO3)(2) crystals

A series of BaxSr1-x(NO3)(2) crystals have been grown from aqueous solutions with different initial Ba2+/Sr2+ ratios. These crystals were characterized by powder X-ray diffraction. All diffraction data were well indexed according to the simple cubic structure, and the variation of lattice constants with the concentration of Ba2+ in the crystals accorded quite well to Vegards Law. The composition of the Sr(NO3)(2) crystal doped with Ba2+ was studied with an electron microprobe. It was found that Ba2+ was enriched in the 100 sectors. The quality of the crystals with different composition. estimated by the high-resolution X-ray diffraction indicated that the second cation added to the crystalline phase degrades the crystalline quality of the crystals. Equilibrium behavior in the Ba(NO3)(2)-Sr(NO3)(2)-H2O system was analyzed using Lippmanns phase diagram, and the equilibrium distribution coefficient D-Ba = 769.2. This large value of D indicates that the Ba2+ ion is drastically preferentially partitioned towards the solid phase

STRUCTURE OF SRXBA3-X(B3O6)2 IN A SOLID-SOLUTION

SrxBa3-x(B3O6)2 where x = 1.16, M(r) = 611.2, trigonal, R3BARc, a = 7.162 (1), c = 37.235 (7) angstrom, V = 1653.9 angstrom 3, Z = 6, D(x) = 3.68, D(m) = 3.67 g cm-3 (using specific gravity bottle and toluene), Mo K-alpha, lambda = 0.71073 angstrom, mu = 119.9 cm-1, F(000) = 1639, T = 296 K, R = 0.031 for 311 unique reflections with I > 3-sigma(I). The structure is isostructural with the high-temperature phase of alpha-Ba3(B3O6)2. Sr2+ ions are located at the 6(a) positions with full occupancy and also share, statistically, the 12(c) positions with Ba2+ ions. The solid solution is stable down to room temperature without a phase transition.

Thermodynamic treatment of the CuO-Y2O3 binary system

Abstract The phase diagram of CuO-Y2O3 was calculated by use of a regular solution model. The interaction parameter was derived from reliable experimental data. The phase diagram was constructed after an approximate treatment of the decomposition of CuO at high temperatures. The calculated results were compared with experimental data.

Optimization of the BaB2O4-Na2B2O4 and BaB2O4-K2B2O4 binary phase diagrams

Abstract The enthalpy of fusion of barium inelaborate was estimated from the limiting slopes of liquidus of BaB 2 O 4 -Na 2 B 2 O 4 and BaB 2 O 4 -K 2 B 2 O 4 systems. The optimized thermodynamic data for these two systems were derived from experimental phase diagrams. In optimization, the ionic fractions and equivalent fractions were introduced for representing ideal mixing entropy and excess Gibbs free energy.