Isothermal sintering, microstructure and superconducting properties of Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7-x} compound

Abstract

Polycrystalline Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7{minus}x} was prepared by the solid state reaction method and characterized by x-ray powder diffraction method, Meissner effect, resistivity by four probe method and iodometric titrations. The material was processed at 930C and isothermal sintering behavior up to 96 was studied using positron lifetime, x-ray powder diffraction (SEM), four probe method for resistivity and critical current vs magnetic field and differential thermal analysis (DTA). Two types of grain morphology are, observed by SEM, one below 36 and one above 36 sintering. DTA show one peak around 954C, above 36 sintering. Positron lifetime results reveal that the lifetime values and {tau}{sub 1} and {tau}{sub 2} arise from positron trapping in strained/deformed regions and-microvoids formed in the triple defect junctions (TDJ), respectively. Size of defect responsible for the pinning centers is estimated from positron lifetime data. Reasons for the lesser value of transport J{sub c} (24.72 A/cm{sup 2}), obtained in the compound sintered at 930C are explained. Nature of defects related to the resistivity component in the compound is also discussed.