Search

Abstract: The subsolidus phase relations of the SrO–REO x –CuO (RE=Ce, Pr, Tb) systems were investigated in air. The samples were equilibrated at 1173K. In the SrO–CeO2–CuO system, there are neither ternary oxide compounds nor ternary solid solutions. However, the slight solubility of Sr into CeO2 results in the formation of a two-phase region, where Ce1−x Sr x O2−δ is in equilibrium with the Sr14Cu24O41−δ phase. The SrO–PrO x –CuO system contains four stable ternary oxide phases: Pr1.4Sr0.4CuO4−δ , Pr7Sr8Cu2O x , Pr1.85Sr1.15Cu2O6−δ and Pr2−x Sr1+x Cu2O6−δ (0.8≤ x ≤0.9). Two binary oxide compounds form ternary solid solutions extending into the pseudo-ternary sections: Pr2−x Sr x CuO4−δ (0.00≤ x ≤0.05) and Sr14−x Pr x Cu24O41−δ (0.0≤ x ≤6.0). The Sr14−x Tb x Cu24O41−δ solid solution (0.0≤ x <6.0) is the only ternary phase formed in the SrO–TbO x –CuO system. This system is dominated by the SrTbO3 phase, which is in equilibrium with all the other compounds. [Copyright &y& Elsevier]

Abstract: The subsolidus phase relations of the SrO–RE2O3–CuO (RE=Tm, Lu, Sc) systems were investigated in air. The samples were synthesised at 900°C. The Sr14−x RE x Cu24O41−δ solid solution was the only ternary phase formed for RE=Tm and Lu. The solubility limit of Sc in the Sr14Cu24O41−δ phase is extremely low and substitution may take place on the Cu sites rather than on the Sr sites. The three systems comprise 6 three-phase regions and there are 2 two-phase regions in the systems including Tm and Lu. The structure of the SrO–Tm2O3–CuO and SrO–Lu2O3–CuO systems is similar to the one of the SrO–Yb2O3–CuO and SrO–Er2O3–CuO systems. There are however, significant differences in the SrO–Sc2O3–CuO system. [Copyright &y& Elsevier]

Abstract: The subsolidus phase relations of the SrO–Er2O3–CuO system were investigated in air. The samples were synthesised at 900°C. The Sr14-xErxCu24O41-δ solid solution was the only ternary phase formed. The system is divided into six three-phase regions and two two-phase regions. Its structure is similar to that of the SrO–Yb2O3–CuO system but the solubility limit of Er in Sr14-xErxCu24O41-δ is significantly higher and amounts to x ≉ 4.5. [Copyright &y& Elsevier]

It is demonstrated how a novel X-ray diffraction method can provide information on the structural dynamics of the individual grains inside a Bi-2223/Ag tape. A microfocused beam of 80 keV X-rays provides both the necessary spatial resolution and penetration power for in situ studies. In a feasibility study at the European Synchrotron Radiation Facility a green mono-filamentary tape is annealed in air for 12 h at 838.5 °C. The Bi-2212 to Bi-2223 transformation is found to be a dynamical process during which individual Bi-2212 grains form, dissociate and “recrystallise” at different times throughout the annealing. The typical reaction time is 1 h. The potential of the method for classifying grains according to orientation, volume and stoichiometry is discussed. [Copyright &y& Elsevier]

Highlights: [•] The phase equilibria of the SrO–Sb2O4–CuO system are determined at 1140K in air. [•] The system contains 7 binary oxides and 1 ternary oxide phase. [•] A new compound with Sr3Sb2CuO9 composition is described. [ABSTRACT FROM AUTHOR]

Cu5SbO6 is found to have a monoclinic, Delafossite-derived structure consisting of alternating layers of O-Cu(I)-O sticks and magnetic layers of Jahn-Teller distorted Cu(II)O6 octahedra in an edge sharing honeycomb arrangement with Sb(V)O6 octahedra. This yields the structural formula Cu(I)3Cu(II)2Sb(V)O6. Variants with ordered and disordered layer stacking are observed, depending on the synthesis conditions. The spin 1/2 Cu2+ ions form dimers in the honeycomb layer. The magnetic susceptibility measured between 5 and 300 K is characteristic of the presence of a singlet-triplet spin gap of 189 K. High resolution synchrotron X-ray diffraction studies indicate that changes in the intra- or interdimer distances between 300 and 20 K, such as might indicate an increase in strength of the Peierls-like distortion through the spin gap temperature, if present, are very small. A comparison to the NaFeO2-type Cu2+ honeycomb compounds Na3Cu2SbO6 and Na2Cu2TeO6 is presented. [ABSTRACT FROM AUTHOR]

Abstract: The influence of Pb-rich phases of precursor powder on microstructural evolution during the first heat treatment of the silver-sheathed (Bi,Pb)2Sr2Ca2Cu3O x ((Bi,Pb)-2223/Ag) superconducting tapes was studied by means of in situ synchrotron X-ray diffraction. Three monofilament tapes were fabricated using precursor powders containing different Pb-rich phases. Sintering was carried out at a fixed temperature of 830°C in 8.5% O2. The phase transitions, structure changes and texture evolution in (Bi,Pb)-2223/Ag tapes were carefully analyzed, and the evolution of different Pb-rich phases, such as Ca2PbO4 and Pb3Sr2.5Bi0.5Ca2CuO y (3321), was discussed. It was found that tapes fabricated using the precursor with the (Bi,Pb)-2212 phase exhibited higher (Bi,Pb)-2223 formation rate than tapes fabricated using the precursors with Pb-rich phases. Texture evolution indicates that texture of the (Bi,Pb)-2212 phase formed in the thermomechanical process depends strongly on the Pb-rich phases of the precursor powders, while the texture of the new formed (Bi,Pb)-2223 grains for all three tapes follows the texture of (Bi,Pb)-2212 grains, and the final (Bi,Pb)-2223 and (Bi,Pb)-2212 textures are approximately identical. A higher texture degree of (Bi,Pb)-2223 grains was achieved in tapes fabricated using the precursors with 3321 or Ca2PbO4 phases. [Copyright &y& Elsevier]

A series of polycrystalline samples of Mg1−x(Zn0.5Al0.5)xB2 (0&les;x&les;0.8) were prepared by solid state reaction method and their structure, superconducting transition temperature (Tc) and transport properties were investigated by means of X-ray diffraction (XRD), ac susceptibility, magnetization and resistivity. The double doping leads to decreases in both the lattice parameters a and c, and the Tc decreases with increasing dopant content. A systematical comparison with Al doped- and Li, Al double doped MgB2 of structure, superconducting transition and critical current density (Jc) is made. It is suggested that the chemical pressure effect plays a more important role influencing the normal state transport and Tc than the change of carrier concentration, and the introduction of disorder into the Mg layers shows little influence improving the irreversibility field and Jc. [Copyright &y& Elsevier]

A series of polycrystalline samples of Mg1−x(Al0.5Li0.5)xB2 (0&les;x&les;0.6) were prepared by a solid state reaction method and their structure, superconducting transition temperature and magneto-transport properties were investigated by means of X-ray diffraction (XRD), ac-susceptibility and resistance in varied magnetic fields. The double doping leads to decreases in both the lattice parameters a and c. The superconducting transition temperature (Tc) decreases with double doping, but the Tc is systematically higher than that of the single Al-doped samples. It is suggested that the hole band filling has little effect on Tc at high doping level, while the disorder induced by doping plays an important role in suppressing Tc. A systematic comparison with Al-doped MgB2 of the structure, superconducting transition and irreversibility field is made. [Copyright &y& Elsevier]

YBCO/Ag tapes prepared using nanosized YBCO powder are currently the best powder-in-tube YBCO tapes with their Ic=5.02 A and Jc=3300 A/cm2 in self-field and at 77 K. The texture of these tapes was studied by removing the silver with mercury and then measuring the texture of the surface with X-ray diffraction. A clear correlation between Ic and c-axis texture is found and even some evidence of ab-texturing in the very best tapes. Less texture is found when the middle of the filament is exposed by cutting the tape. This suggests that multifilament tapes with smaller filament cross-section should have even higher Ic. [Copyright &y& Elsevier]