Influence of hole filling by Hf and hole doping by Ca on the superconductivity and flux pinning of YBa2Cu3O7−δ

R. G. Kulkarni; I. A. Shaikh; J. A. Bhalodia; G. J. Baldha; D. G. Kuberkar

doi:10.1103/PhysRevB.49.6299

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Influence of hole filling by Hf and hole doping by Ca on the superconductivity and flux pinning of YBa2Cu3O7−δ

R. G. Kulkarni, I. A. Shaikh, J. A. Bhalodia, G. J. Baldha, D. G. Kuberkar

DOI 10.1103/PhysRevB.49.6299 · Physical Review B

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Abstract

The structural and superconducting properties of (Y1−x−yCayHfx)Ba2Cu3Oz samples are investigated using resistivity, ac susceptibility, and dc magnetization measurements. The effect of increasing the Hf concentration in Y1−xHfxBa2Cu3Oz lowers the oxygen content and decreases Tc. The substitution of Ca for Y in (Y0.85−yCayHf0.15)Ba2Cu3Oz provides proper matching between the ionic radius and valence of Y3+ (0.89 Å) and the average ionic radius and valence of Hf4+ (0.78 Å) and Ca2+ (0.99 Å). As the Ca content increases, the Tc increases from y=0 (74 K) to y=0.15–0.20 (compensated oxides) having Tc of 84.5–85.5 K. Magnetization measurements on powdered Hf-doped samples exhibit pronounced M(H) hysteresis loops indicative of extensive flux pinning and enhanced critical currents.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
YBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	90	Pressure not reported	unknown
YBa2Cu3Oz Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	90	Pressure not reported	unknown
Y0.95Hf0.05Ba2Cu3Oz Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	86	Pressure not reported	midpoint
Y0.90Hf0.10Ba2Cu3Oz Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	81	Pressure not reported	midpoint
Y0.85Hf0.15Ba2Cu3Oz Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	74	Pressure not reported	midpoint
Y0.80Hf0.20Ba2Cu3Oz Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	70	Pressure not reported	midpoint
(Y0.80Ca0.05Hf0.15)Ba2Cu3Oz Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	76.5	Pressure not reported	midpoint
(Y0.75Ca0.10Hf0.15)Ba2Cu3Oz Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	81	Pressure not reported	midpoint
(Y0.70Ca0.15Hf0.15)Ba2Cu3Oz Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	84.5	Pressure not reported	midpoint
(Y0.65Ca0.20Hf0.15)Ba2Cu3Oz Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	85.5	Pressure not reported	midpoint