A systematic study of yttrium substitution for calcium in the high-temperature superconductor Bi2Sr2CaCu2O8 compound has been performed. The samples of Bi2Sr2Y x Ca1−x Cu2O8 have been prepared by the sintering standard procedure using oxides and carbonates as precursors, weighted to obtain the nominal composition with 0≤x≤1. The real stoichiometric composition of the pellets and uniformity of the samples has been verified by EDS analysis. The grain dimension (≈1 μm) and the good pellet compactness have been established by SEM morphologic observation. By X-ray diffraction analysis the crystalline structure of orthorhombic type has been established. By increasing the yttrium concentration the resistivity dependence on temperature goes from metallic to insulating behaviour. For the superconductive samples T c decreases for increasing doping percentage. Thick films on MgO substrates of Bi2Sr2CaCu2O8 have been obtained by melting-quenching-annealing procedure. These films showed critical temperatures higher than the pellets.
Preparation and characterization of sintered pellets and «Thick» films of Bi2Sr2YxCa(1−x)Cu2O8
CAROTENUTO, Maurizio;DI LEO, Rosario;NIGRO, Angela;ROMANO, Paola;CUCOLO, Anna Maria
1994-01-01
Abstract
A systematic study of yttrium substitution for calcium in the high-temperature superconductor Bi2Sr2CaCu2O8 compound has been performed. The samples of Bi2Sr2Y x Ca1−x Cu2O8 have been prepared by the sintering standard procedure using oxides and carbonates as precursors, weighted to obtain the nominal composition with 0≤x≤1. The real stoichiometric composition of the pellets and uniformity of the samples has been verified by EDS analysis. The grain dimension (≈1 μm) and the good pellet compactness have been established by SEM morphologic observation. By X-ray diffraction analysis the crystalline structure of orthorhombic type has been established. By increasing the yttrium concentration the resistivity dependence on temperature goes from metallic to insulating behaviour. For the superconductive samples T c decreases for increasing doping percentage. Thick films on MgO substrates of Bi2Sr2CaCu2O8 have been obtained by melting-quenching-annealing procedure. These films showed critical temperatures higher than the pellets.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
