Superconducting lead cuprates (Pb0.5Cu0.5)(Sr1−yBay)2(Y1−xCax) Cu2Ow

Shin-ichi Koriyama; Toshihiko Maeda; Kazuhiro Sakuyama; H. Yamauchi; Shoji Tanaka

doi:10.1103/PhysRevB.45.7424

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Superconducting lead cuprates (Pb0.5Cu0.5)(Sr1−yBay)2(Y1−xCax) Cu2Ow

Shin-ichi Koriyama, Toshihiko Maeda, Kazuhiro Sakuyama, H. Yamauchi, Shoji Tanaka

DOI 10.1103/PhysRevB.45.7424 · Physical Review B

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Abstract

The effects of Ba substitution for Sr and Ca substitition for Y on superconducting properties of lead cuprates, (Pb0.5Cu0.5)Sr2YCu2O7 (the ‘‘1:2:1:2’’ phase), are investigated. The parent material of these cuprates, i.e., (Pb0.5Cu0.5)Sr2YCu2O7, is found to have few charge carriers and, therefore, does not exhibit superconductivity at a temperature above 4.2 K. A sample in which Sr is substituted by Ba has a small amount of holes but yet does not exhibit superconductivity above 4.2 K. A sample in which both Sr and Y are substituted, respectively, by Ba and Ca contains more holes than the one in which only Ba substitution for Sr is made. This sample exhibits superconductivity with the superconducting onset temperature as high as 25 K. For superconducting lead cuprates of the 1:2:1:2 phase, the charge carriers are found to be holes according to Hall-coefficient measurements. The Ba substitution for Sr is found to contribute to the increase in hole concentration through two different mechanisms: (1) It extends the solubility limit of Ca in the Y sites when the [Pb]/[Cu] ratio is fixed in the (Pb,Cu)O rocksalt-type plane; (2) it changes the valency from 2+ to 1+ of a portion of the Cu ions in the (Pb,Cu)O plane.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
(Pb0.5Cu0.5)(Sr1-yBay)2(Y1-xCax)Cu2Ow Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	25	Pressure not reported	onset
(Pb0.5Cu0.5)Sr2YCu2O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
(Pb2Cu)Sr2(Y,Ca)Cu2O8 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	70	Pressure not reported	unknown
(Pb0.5Sr0.5)Sr2(Y0.5Ca0.5)Cu2O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
(Pb,Cu)(Sr,Ba)2(Y,Ca)Cu2O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	60	Pressure not reported	onset
(Pb,Cu)Sr2(Y,Ca)Cu2O Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	52	Pressure not reported	onset