Oxy-anion (PO3- 4) substituted phases of the composition REBaSrCu2.8(PO4)0.2Oy have been synthesized. Single phase formation is achieved only for the larger rare earths (La → Ho and Y) and all the phases crystallize in the tetragonal 123 structure. IR studies confirm the presence of a phosphate group in the structure. The total oxygen content (including that associated with the oxy-anion PO3- 4) has been found to be in the range 7.01 to 7.10 per formula unit. Except for RE = La, Nd, Yb and Lu, all the phases exhibit superconductivity and the Tc,zero values vary from 18 to 38 K. The 7c,zero increases with decreasing size of RE3+. ErBaSrCu3O7 is multiphasic and single phase formation is achieved for the first time by phosphate substitution at the copper site. Single phase formation is encountered for x = 0.10 and 0.15 with Tc,zero values of 54 and 37 K respectively. © 1997 Elsevier Science B.V.

Mamidanna Sri Ramachandra Rao

Department Of Physics

Upadhyayula V Varadaraju

Department Of Chemistry

Karthikeyan N. Marimuthu

Composition effects

Crystal Structure

Crystallization

High temperature superconductors

infrared spectroscopy

Magnetic permeability

Phase Transitions

Phosphates

RARE EARTH COMPOUNDS

Substitution reactions

Superconductivity

Synthesis (chemical)

OXY ANION SUPERCONDUCTORS

SINGLE PHASE FORMATION

Oxide superconductors

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IIT Madras

Phase formation and superconductivity in REBaSrCu3−x(PO4)xOy (0 ≤ x ≤ 0.3)

Physica C: Superconductivity and its Applications

The structure of a newly stabilized superconducting phase ErgaSrCu2.9(PO4)0.1O(y) was studied by means of electron microscopy and powder neutron diffraction. The electron microscopy study on ErBaSrCu2.9(PO4)0.1O(y) revealed the existence of a tweed-like structure. Rietveld refinement was carried out on ErBaSrCu(3-x)(PO4)(x)O(y) (x = 0.0, 0.10, and 0.20) with the orthorhombic space group Pmmm. Substitution of the phosphate group at the copper site in ErBaSrCu(3-x)(PO4)(x)O(y) influenced Cu(2)-O planes strongly. (C) 2000 Academic Press.

Journal of Solid State Chemistry

Electron microscopy and neutron diffraction studies on ErBaSrCu3(-x)(PO4)(x)O(y) (X = 0.0, 0.10, 0.20)

The title compounds have been synthesized and studied with a view to stabilize the 123 structure and achieve single phase formation. Single phase and high TC are obtained with Sr content as low as x=0.1 in the case of Yb. The single phase region extends only up to x=0.5, in contrast to the Sr substituted Y-123 system wherein the single phase region has been established up to x=1.2. The TC, zero decreases systematically with increase in x. Preliminary results of thermopower on two of the single phase compounds (x=0.1 and 0.2) show a negative thermopower at all temperatures above TC with temperature dependence similar to that of Y-123. In the case of Lu, Sr substitution does not completely stabilise the 123 phase for any x. However, the quantity of the 123 phase is increased significantly for x=0.4 -0.5 when compared to x=0.0. Structural, electrical and magnetic data are discussed. © 1992.

Materials Research Bulletin

Structure and superconductivity studies on LnBa2-xSrxCu3O7 (Ln=Yb and Lu; 0.0≤x≤0.5)

We report a strong rare-earth size dependence of (Formula presented) in R(Formula presented)(Formula presented)(Formula presented)(Formula presented) (R=rare earth, z≊7.2) compounds, unlike in R(Formula presented)(Formula presented)(Formula presented) compounds. A strong correlation is observed between the superconducting transition temperature and the orthorhombicity of the structure, which itself is R-size dependent. Orthorhombicity is highest for (Formula presented)(Formula presented)(Formula presented)(Formula presented) and (Formula presented)(Formula presented)(Formula presented)(Formula presented) compounds, which also have yielded the highest (Formula presented) (≊42 K). Significantly, (Formula presented)(Formula presented)(Formula presented)(Formula presented) stabilizes in a 1-2-3 structure and also superconducts ((Formula presented)≊22 K), whereas (Formula presented)(Formula presented)(Formula presented)(Formula presented) does not superconduct, although it forms a single phase. © 1996 The American Physical Society.

Physical Review B - Condensed Matter and Materials Physics

Strong rare-earth size dependence

A single-phase Sr-based Tb-123 phase has been synthesized by chemical stabilization. TbSr2Cu2.85Re0.15O 7+δ exhibits superconductivity at Tc,zero=22 K. X-ray diffraction results suggest a relatively small orthorhombicity and neutron diffraction studies indicate an excess oxygen content (≥7.2) in the sample. Tb is present as a trivalent ion in the superconducting phase as derived from x-ray photoelectron spectroscopy.© 1995 American Institute of Physics.

Applied Physics Letters

Stabilization of a superconducting TbSr2Cu2.85Re 0.15O7+δ compound and the valence state of terbium

Physica C: Superconductivity

Chemistry and structure of borate-containing materials LnSr2Cu3-xBxO7-δ

Oxyanion derivatives of cuprate superconductors superconducting 123 phosphates

Phase formation and superconductivity in REBaSrCu3-x(PO4)xOy (0 ≤ x ≤ 0.3)

Journal	Data powered by TypesetPhysica C: Superconductivity and its Applications
Publisher	Data powered by TypesetElsevier
ISSN	09214534
Open Access	No