Phase Equilibria and the Effect of Processing on the Electrical Transport and Magnetic Properties of (Pb1—yCdy)Sr2(Y1—xCax)Cu2O7—δ
作者:T. P. Beales、J. M. Parberry
DOI:10.1002/1521-396x(199708)162:2<689::aid-pssa689>3.0.co;2-j
日期:1997.8
We have prepared polycrystalline (Pb0.5Cd0.5)Sr-2(Y1-xCax)Cu2O7-delta (0.0 less than or equal to x less than or equal to 0.5) powder samples and determined the single phase region using X-ray diffraction. Substitution of Y for lanthanide elements and Cd for an M-II metal with an effective cationic size close to 0.1 nm to produce single phase samples is possible for x = 0.0. Superconductivity in x = 0.0 samples is optimised (T-cmax = 60 K) after a high pressure oxygen anneal. For x > 0.0 samples, the single phase region exists up to a value of x = 0.15. The highest T-c = 92 K occurs at the nominal x = 0.3 composition. Rietveld analysis of the x = 0.3 material shows that prescence of calcium in the rock salt layer resulting in a stoichiometry of (Pb0.5Cd0.392Ca0.108)Sr-2(Y0.864Ca0.136)Cu2O7-delta with (Ca0.45Cd0.55)O as an impurity phase.