Two new HgSr cuprate superconductors

• Published in: Physica. C, Superconductivity Superconductivity, 1994-12, Vol.235, p.903-904
• Main Authors: Morris, D.E., Singh, K.K., Kirtikar, V., Sinha, A.P.B.
• Format: Article
• Language: English
• ISSN: 0921-4534; 1873-2143
• DOI: 10.1016/0921-4534(94)91676-4

Two new series of HgSr cuprate superconductors: (a) (Hg, Mo) Sr 2CuO 4+δ and (b) (Hg,Bi)Sr 2(Ca,Y)Cu 2O 7−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. T c, however, is substantially reduced as compared to the corresponding unsubstituted HgBa cuprate superconductor. The best T c in series (a) is 78 K for (Hg 0.85Mo 0.15)Sr 2CuO 4+δ and that in series (b) is 92 K for (Hg 0.67Bi 0.33)Sr 2(Y 0.5Ca 0.5)Cu 2O 7−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 T c 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 T c results from the presence of these extra oxygens in the Hg later.