PREPARATION AND CHARACTERIZATION OF SINTERED PELLETS AND THICK-FILMS OF BI2SR2YXCA1-XCU2O8

A systematic study of yttrium substitution for calcium in the high-tem perature superconductor Bi2Sr2CaCu2O8 compound has been performed. The samples of Bi2Sr2YxCa1-xCu2O8 have been prepared by the sintering sta ndard procedure using oxides and carbonates as precursors, weighted to obtain the nominal composition with 0 less than or equal to x less th an or equal to 1. The real stoichiometric composition of the pellets a nd uniformity of the samples has been verified by EDS analysis. The gr ain dimension (approximate to 1 mu m) and the good pellet compactness have been established by SEM morphologic observation. By X-ray diffrac tion analysis the crystalline structure of orthorhombic type has been established. By increasing the yttrium concentration the resistivity d ependence on temperature goes from metallic to insulating behaviour. F or the superconductive samples T-c decreases for increasing doping per centage. ''Thick'' films on MgO substrates of Bi2Sr2CaCu2O8 have been obtained by melting-quenching-annealing procedure. These films showed critical temperatures higher than the pellets.