The effects of composition, synthesis conditions, oxygen content and F doping on superconductivity and structure for R-substituted Bi-2201

Abstract

The effects of composition, synthesis conditions, oxygen content and F doping on superconductivity and structure for the R-substituted Bi-2201 compound was investigated by means of XRD and measurements of superconductivity. For the Bi 1.95 Sr 2.05−x R x CuO 6+y compound (R = La, Pr, Nd and Sm), the optimum value of x for T c is x = 0.4. When x = 0.4, the optimum sintering temperature is 840 • C for R = La, Pr and Nd, 820-830 • C for R = Sm. T c decreases with decreasing the ionic radius of R. For Bi 1.95 Sr 1.65 La 0.4 CuO 6+y , the optimum range of oxygen content is y = 0.28-0.33 and the superconductivity is improved by quenching. For F-doped Bi-2201, T c decreases with increasing F content.

Anisotropic resistivity in epitaxial films grown on tilted (001) substrate

“…Previous studies reported that the T c of Bi-2201 is about 6-10 K in a very narrow range of Bi:Sr ratio [1]. Partial substitution of Sr by large atomic radius rare-earth elements such as La or Nd expands the superconducting range and also increases T c to 24-35 K [2,3]. When added La, the BiSrLaCuO system easily becomes superconducting, and the optimum substitution of La for Sr was shown to be 0.4 [4,5].…”