SYNTHESIS AND O-17 NMR CHARACTERIZATION OF THE HIGH T(C) PHASE IN THE BI-PB-SR-CA-CU-O SUPERCONDUCTOR

Abstract

A single-phasic polycrystalline sample of superconductor Bi1.8Pb0.4Sr2Ca2Cu3Oy ( T(c) = 108K) was obtained by reaction of prereacted Bi1.8Pb0.2Sr2Ca2Cu3Oy with PbO under low oxygen pressure, which was fully characterized by X-ray diffraction and measurements of electrical resistivity and magnetic susceptibility. O-17 NMR measurements have been performed for the compound at 300 K. Spectrum of the Bi1.8Pb0.4Sr2Ca2Cu3Oy compound contained two distinctive peaks in the paramagnetic region, in which a broad resonance at 2150 ppm and a relatively sharp peak at 1600 ppm were assigned as the oxygens of two outer CuO2 planes and a central CUO2 layer, respectively. In the diamagnetic region a series of peaks were observed about 350 ppm, which are more likely to be associated with the oxygen resonance of the SrO plane. The BiO resonance expected from the BiO plane appears to be smeared out, which might be attributed to the incommensurate modulation and nonperiodic oxygen position of the Bi2O2 layers.