Two new Hg---Sr cuprate superconductors

Morris, D. E. ; Singh, K. K. ; Kirtikar, V. ; Sinha, A. P. B. (1994) Two new Hg---Sr cuprate superconductors Physica C: Superconductivity, 235-240 (2). pp. 903-904. ISSN 0921-4534

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Official URL: http://www.sciencedirect.com/science/article/pii/0...

Related URL: http://dx.doi.org/10.1016/0921-4534(94)91676-4

Abstract

Two new series of Hg---Sr cuprate superconductors: (a) (Hg, Mo) Sr2CuO4+δ and (b) (Hg,Bi)Sr2(Ca,Y)Cu2O7-δ have been synthesized. Hg---Sr superconductors, which are otherwise difficult to make, have been stabilized by partial substitution of higher-valent cations for Hg. Tc, however, is substantially reduced as compared to the corresponding unsubstituted Hg---Ba cuprate superconductor. The best Tc in series (a) is 78 K for (Hg0.85Mo0.15)Sr2CuO4+δ and that in series (b) is 92 Kfor(Hg0.67Bi0.33)Sr2(Y0.5Ca0.5)Cu2O7-δ as compared to 95 K and 125 K respectively for the corresponding unsubstituted Hg---Ba cuprates. In both series, high p(O2) annealing lowers the Tc even further suggesting that the samples are overdoped and the substitution of higher-valent cation for Hg did not decrease the hole concentration. Addition of Mo/Bi appears to be accompanied by the uptake of additional oxygen, δ , which go to the Hg-Oδ layer and the lowering of Tc results from the presence of these extra oxygens in the Hg later.

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