Crystals of Sr3NiPtO6 and Sr3CuPtO6 were grown from a K2CO3 flux containing SrCO3, NiO or CuO, and Pt metal powder, at 1150 °C. The structure of Sr3NiPtO6 was solved by means of single-crystal X-ray diffraction analysis. The structure was refined in space group R3c, with a = 9.5832(1) A and c = 11.1964(1) A. Sr3CuPtO6 and Sr3NiPtO6 are structurally related to the parent compound, A4PtO6 (A = Ca, Sr, Ba), and contain infinite chains of alternating, face-sharing PtO6 octahedra and A‘O6 (A‘ = Ni, Cu) trigonal prisms. Magnetic measurements were carried out on both samples using 3−5 mm long single crystals. Magnetic susceptibility studies on oriented single crystals of Sr3NiPtO6 indicate the presence of Ni(II) ions with a large single-ion anisotropy (D = 93.7(5) K, g∥ = 2.143(6), and g⊥ = 2.392(4)). In contrast, Sr3CuPtO6 exhibits S = 1/2 Heisenberg linear chain antiferromagnetism with J/k = −24.7(1) K, J‘/k = −7.3(8) K, g∥ = 2.127(6), and g⊥ = 2.150(6).

Crystal Growth and Magnetic Measurements on Aligned Single Crystals of the Oxides Sr3NiPtO6 and Sr3CuPtO6

The authors present results of precise measurements of the thermal conductivity lambda of a non-superconducting sample of Y-Ba-Cu-O in the temperature range 1-300 K. Heating and cooling curves of lambda (T) exhibited clear hysteresis effects between 80 and 240 K, not previously reported. The temperatures at which the thermal conductivity anomalies appear were the same or close to those at which other anomalies were observed in superconducting samples. The results can be explained qualitatively if one assumes that the 1:2:3 phase is a spinodal decomposition mixture of two phases with different stoichiometry with respect to oxygen content and that a change in lattice dimensions takes place at about 80 K.

http://iopscience.iop.org/article/10.1088/0953-2048/1/6/004/pdf

Thermal conductivity of the Y-Ba-Cu-O tetragonal structure: phase transitions and hysteresis behaviour

In this paper we report our results on the effect of Sb-doping on the superconducting properties of the compound Bi 1.6- x Sb x Pb 0.4 Sr 2 Ca 2.2 Cu 3.5 O y for x =0.0, 0.1 and 0.2. Through a series of experiments it is shown that the small addition of Sb ( x =0.1) increases the 2223 phase fraction and enhances T c as well as intergrain J c , provided that the sintering parameters are carefully optimized. Thus, for example, the composition Bi 1.5 Sb 0.1 Pb 0.4 Sr 2 Ca 2.2 Cu 3.5 O y sintered at 830°C for 12 h has a T c0 (zero resistivity) = 108 K, a drop in the χ'- T plot at 108 K and in intergrain J c =695 A/cm 2 (as estimated on the basis of Clem's model). Any lowering of sintering temperature below 830°C or prolonging of sintering at 830°C leads to a degradation in the superconducting parameters. Similarly, a reduction in T c and J c is observed if Sb concentration is increased to 0.2. The sintering parameters (temperature and duration) thus appear to be critical for a given composition.

Effect of Sb doping on critical current density in Bi (Pb)-Sr-Ca- Cu-O high-Tc superconductors

In an attempt to increase the volume fraction of the high Tc phase Bi2Sr2Ca2Cu3Oy(2223), mixed doping of Pb+Sb was performed in a Bi superconducting system. A stoichiometric starting composition with Bi partially replaced by Sb+Pb was found to result in a system with an unusually high value (>or=140 K) of onset transition temperature (Tcon). A Tco of 111 K could be achieved with about 75 to 80% 2223 content, as calculated from the XRD data, for annealing duration of about 100 h, which is much less than in an undoped or Pb-doped Bi system. The most important characteristic of this system is the presence of a 'new phase' with its strong and sharp reflections near 2 theta =30 degrees in the XRD pattern. Such a phase could never be detected in the Bi system doped only with Pb. Interestingly, the 'new phase' is found to be present even in the calcined material and its existence has been shown at all stages of annealing. R-T characteristics and XRD analysis have revealed the development of the low Tc phase Bi2Sr2Ca1Cu2Oy (2212) at a very early stage of annealing, and further the transformation of 2212 into 2223, always in coexistence with the 'new phase' and CuO. Incorporation of Sb resulting in the formation of the 'new phase' appears to be responsible for Tcon values that are unusually high and also for making the kinetics of the solid state reaction of 2223 formation much faster.

http://iopscience.iop.org/article/10.1088/0953-2048/4/1/003/pdf

Enhancement of Tcon, appearance of a 'new phase' and faster kinetics in Pb+Sb doped Bi2Sr2Ca2Cu3Oy

The morphological and compositional changes of the Pt-based phase in melt-grown Y-Ba-Cu-O samples grown on the Al2O3 substrate were studied. It was shown that Al dissoluted in the melt is effectively consumed by the Pt-based phase, by replacing Cu with Al until it becomes fully converted to the Pt, Al-based phase. Al substitution changes irregular shape of Pt-based particles into Pt, Al-based crystals with well-developed habits. Ag addition hinders Al diffusion into the Y-Ba-Cu-O sample during melt processing.

https://iopscience.iop.org/article/10.1088/0953-2048/15/2/306/pdf

Morphology and composition changes of the Pt-based secondary phase in melt-grown YBCO caused by Al pollution

The Tc=140 K superconductor Bi2Sr2Ca2Cu3O10- delta doped with Sb and Pb was characterised by powder X-ray diffraction, electron diffraction and electron probe microanalysis. It was observed in the specimen that there was a new phase Bi3Sb0.8Pb0.2Sr4.1Ca3.9CuO15+ delta besides 2212, 2223 and a little CuO. The new phase belongs to the monoclinic system with cell dimensions a=22.14, b=5.902, c=19.91 AA and beta =99.7 degrees .

https://iopscience.iop.org/article/10.1088/0953-2048/3/2/008/pdf

Phase identification of 140 K superconducting Bi2Sr2Ca2Cu3O10-δ doped with Sb and Pb

Structure study of Ba2CeCu3O7.4

Superconducting single crystals of Bi-Sr-Ca-Cu-O 2212 phase have been successfully grown by a directional solidification method. The maximum size of single crystals reached 19×3×2 mm 3 . The (001) plane of the crystals is parallel to the growth direction. The crystals tend to grow along the [010] direction. The back-reflection Laue pattern revealed that the large crystal is indeed one single crystal. Measurements of electrical resistivity and ac susceptibility showed that T c (zero) of the single crystal annealed in O 2 was 81.5 K

DIRECTIONAL GROWTH OF Bi -Sr-Ca-Cu-O2212 PHASE SUPERCONDUCTING SINGLE CRYSTAL

The single (123) phase of Y-Ba-Cu oxides with T-phase structure was prepared using the air-quenching technique. From the measurements of electrical resistance, thermal expansion coefficience, specific heat, ac susceptibility and XRD, it is the first time to find the existance of a structure phase transition. It is suggested to be a structure phase transition from Y-phase to O-phase. The explanation for low Tc in this system is also proposed in this paper.

Cheng Tingzhu

Papers

Phase identification of 140 K superconducting Bi2Sr2Ca2Cu3O10-δ doped with Sb and Pb

Structure study of Ba2CeCu3O7.4

DIRECTIONAL GROWTH OF Bi -Sr-Ca-Cu-O2212 PHASE SUPERCONDUCTING SINGLE CRYSTAL

The structure phase transition of the quenched YBa2Cu3O7−y with tetragonal phase

Growth and characterization of Ba4Pt1+xCu2−xO9−y single crystal