G.T. Bhandage

structural, electrical and magnetic properties of aluminium-, gallium- and iron-substituted YBa2Cu3O7 − δ

Abstract We present X-ray, resistivity ρ, Hall effect and susceptibility /gc data for YBa 2 Cu 3 − x M x O 7 − δ ( M ≡ Al , Ga , Fe ; 0 x x ≈ 0.1, the structure changes from orthorhombic to tetragonal, although T c > 77 K . The current density derived from the magnetization data decreases faster for aluminium than for iron and gallium.

Accurate determination of the Mössbauer spectrum hyperfine parameters and correlation withT c in YBa2Cu3−x 57Fe x O7−δ (0.01≦x≦0.15)

High statistics room temperature Mössbauer spectra have been performed on ten YBa2Cu3−xFexO7−δ (0.01≦x≦0.15) samples. The different fit solutions (including broadening of the lines) are tested with “χ2” factor analysis. Only two solutions are valid with almost similar parameters. The results on present samples and our previous results on various materials made under different heat treatments show thatTc is governed byx and the relative population of one of the iron species. These species can be related to highly coordinated irons in the chains.

DC susceptibility and magnetization of YBa2Cu3−xFexO7−δ (0<x<0.1)

Abstract X-ray, dc susceptibility and magnetization data of YBa 2 Cu 3−x Fe x O 7−δ (0 86 K. The superconductivity may thus be preserved through the orthorhombic-tetragonal (t) transition which takes place near x = 0.10. The critical current J c derived from the magnetization data decreases very little for x = 0.02 with respect to x = 0. For x>0.02, J c decreases faster than T c does. The effect of heat treatment is pointed out. The data are briefly discussed taking into account the small coherence length and the presence of orthorhombic domains in t phase.

Preparation, electron microscopy and superconductivity of a new class of high Tc superconductors: Pb2Sr2Y1-xCaxCu3O8+δ (x = 0.5; 0.25)

Abstract Preparation, electron microscopy, resistivity (ζ) and field cooled susceptibility (χ) of Pb 2 Sr 2 Y 1- x Ca x Cu 3 O 8+ δ ( x =0.5; 0.25) are reported. They crystallise in an orthorhombic structure. ζ shows a two step transition with distinct onsets at 86 and 45 K with zero resistivity at 15 K. χ data show a diamagnetic onset at 74 K. These data while confirming the results of Cava et al (Nature 336, 211 1988) point out the influence of the preparation conditions on the superconducting properties calling for a systematic study.

Magnetisation of YBaCuO and Pb-substituted BiSrCaCuO

The magnetisation as a function of magnetic field (0<H<15 kOe) and as a function of temperature (9<T<50 K) of YBaCuO and Pb-substituted BiSrCaCuO has been studied. The beneficial effect of Pb addition on the critical current Jc is pointed out. The data also show that the Jc of the Pb-substituted Bi system is comparable to that of sintered YBaCuO. In both these systems, Jc is of the order of 4*106 A cm-2 at 9 K in a field of 2 kOe.

Superconductivity in MBiSrCaCuO (M = Pb, Nd, Sm, Gd)

Abstract We report on the X-ray diffraction, resistivity and magnetic susceptibility (SQUID, H = 5 Oe) data of (M)BiSrCaCuO (M = Pb, Nd, Sm, Gd) system. The nominal compositions studied were (2212), (2223), (4334) and (2224). The superconducting properties are influenced very much by the annealing conditions. For M = Pb (0.4) in (2223) and (2224), a three layer CuO structure (n = 3 with c = 37 A ) appears with the zero resistivity at 100 Tc 10K. Whereas for 10% of M = Nd, Sm, Gd in (2212), (2223) or (2224) a two layer structure ( c = 30 A ) is obtained and Tc is less than 90K. The data seem to indicate the role played by BiO planes as pointed out by band structure calculations.

Transport and magnetic properties of plasma sprayed YBaCuO and BiSrCaCuO

Abstract Electrical and magnetic properties of plasma sprayed YBaCuO and BiSrCaCuO coatings are reported. After proper annealing, they become superconductors respectively at 88.6 and 65 K.

Structural and superconducting properties of Pb2Sr2Ln1−xCaxCu3Oy (Ln = Y, Yb)

Abstract Resistivity, magnetic susceptibility, X-ray, electron diffraction and EDX analyses of the title compound are presented. The preparative conditions for this compound are more stringent than for YBaCuO and BiSrCaCuO.

Detailed Mossbauer studies on YBa2Cu3-xFexO7-† (OT phases) with low iron content

Abstract High statistic Mossbauer spectra have been performed at 300K on ten samples of YBa 2 Cu 3−x Fe x O 7−† (0.01 ≦ x ≦ 0.15). Only two fit solutions hold from χ 2 factor analysis. It is shown that T c is governed by x and by the population of one iron species which could correspond to high coordinated irons in chains.