Eight rare-earth-substituted Pb-based 1:2:1:2 superconducting compounds: (Pb,Cu)Sr2(Ca,R)Cu2O7 (R=Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm)

H. B. Liu; D. E. Morris

doi:10.1103/PhysRevB.44.5369

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Eight rare-earth-substituted Pb-based 1:2:1:2 superconducting compounds: (Pb,Cu)Sr2(Ca,R)Cu2O7 (R=Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm)

H. B. Liu, D. E. Morris

DOI 10.1103/PhysRevB.44.5369 · Physical Review B

T1

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Abstract

Rare-earth substitution has given a series of Pb-based 1:2:1:2 superconducting compounds (Pb,Cu)Sr2(Ca,R)Cu2O7 (R=Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm). Tc’s vary inversely with rare-earth ionic size from 72 K (Tm) to 60 K (Gd) and then remain constant for larger ions up to Nd. This behavior (Tc decreasing for larger ions separating the two CuO2 superconducting sheets) is similar to the behavior of RBa2Cu4O8 (1:2:4) and R2Ba4Cu7Oy (2:4:7), but not RBa2Cu3O7 (1:2:3). As prepared in air the samples were not superconductors; superconductivity was induced by annealing in oxygen under 100 bar of oxygen pressure at 940 °C followed by fast cooling from 940 to 100 °C (50 °C/min). Lattice constants of the compounds correlate with the ionic radii of the rare-earth elements, as in the 1:2:3, 1:2:4, and 2:4:7 compounds.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
(Pb0.5Cu0.5)Sr2(Ca0.5Nd0.5)Cu2O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	60	Pressure not reported	onset
(Pb0.5Cu0.5)Sr2(Ca0.5Sm0.5)Cu2O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	60	Pressure not reported	onset
(Pb0.5Cu0.5)Sr2(Ca0.5Eu0.5)Cu2O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	60	Pressure not reported	onset
(Pb0.5Cu0.5)Sr2(Ca0.5Gd0.5)Cu2O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	60	Pressure not reported	onset
(Pb0.5Cu0.5)Sr2(Ca0.5Dy0.5)Cu2O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	65	Pressure not reported	onset
(Pb0.5Cu0.5)Sr2(Ca0.5Ho0.5)Cu2O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	67	Pressure not reported	onset
(Pb0.5Cu0.5)Sr2(Ca0.5Er0.5)Cu2O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	69	Pressure not reported	onset
(Pb0.5Cu0.5)Sr2(Ca0.5Tm0.5)Cu2O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	72	Pressure not reported	onset
(Pb0.5Cu0.5)Sr2(Ca0.5Y0.5)Cu2O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	67	Pressure not reported	unknown
(Pb0.5Cu0.5)(Sr0.5Ba0.5)2(Y0.6Ca0.4)Cu2Oy Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	63	Pressure not reported	unknown