EFFECT OF Cu ADDITION ON THE SUPERCONDUCTING BEHAVIOR OF La2.xSrxCuOy

D. SERAFINI; J.P. ABRIATA; A. CANEIRO; F. DE LA CRUZ

SOLID STATE COMMUNICATIONS

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 1995 vol. 93 p. 513 - 517

0038-1098

The superconducting behavior of stoichiometric samples of La2_xSrxCuOy, preparedwith an accurate control of cationic composition for X = 0.15, 0.16, 0.17, 0.18, 0.19 and0.20, was studied by ac susceptibility and magnetization measurements. Only the sampleswith X = 0.15 and 0.16 showed a sharp transition at Tco --- 37 K. For higher values of Xthe superconducting transition became broader with a tail beginning at the same Tco.Samples prepared starting from the same batch of ceramic powders for X > 0.17, but withaddition of small excess of CuO, showed the formation of large superconducting grains.These grains have the same Tco= 37 K as the La2_xSrxCuOy stoichiometric samples, andsignificantly sharper transitions. Our results are discussed in terms of the miscibility gapwhich has been proposed to exist for X > 0.16 by previous authors, and the much fasterkinetics of evolution towards equilibrium caused by the existence of a Cu excess.