Nanocrystalline-grained Bi-Sr-Ca-Cu-O and its superconducting property

Abstract

In this paper, the systematic study of nanostruc- tured high-temperature superconducting materials is reported for the first time. Nanocrystalline-grained Bi Sr Ca Cu O was prepared by crystallizing the corresponding amorphous plates. The grain-growth and size-control techniques were studied. The phases occurring were investigated by means of X-ray diffraction, and the morphologies of the grains were observed by electron microscopy. The superconduct- ing properties, measured by resistance-temperature ( R T) and alternating current susceptibility-temperature (ac T) methods, are discussed. Probable research values of these mesoscopic-structured HTSC materials are also proposed. PACS: 74.72.Hs; 81.35.+k; 81.40.-z Since the discovery of high-temperature superconductivity (HTSC), researchers have directed their attention to various polycrystalline and single crystalline samples with large grain sizes (> 3000 nm). The superconductivity of nanocrystalline HTSC material has not been investigated to our knowledge. If the grain size were quite small and located in the meso- scopic range, it is expected that the physical and=or mechan- ical properties of the HTSC materials would no longer be independent of the grain size. The purpose of our research was to prepare the Bi Sr Ca Cu O samples with various grain sizes and study their physical properties. This research will be helpful for both the application of the HTSC materials and the understanding of high-temperature superconductiv- ity. On the basis of our experience of growing the Bi-based 2212 superconducting whiskers from the glassy state (1) and the principle of preparing nanocrystalline alloys by means of crystallization from amorphous alloys (2), we prepared the Bi Sr Ca Cu O samples with various grain sizes. The systematic study of the superconductivities of nanos- tructured high-temperature superconducting materials is re- ported for the first time in this paper. In fact, there have been many reports on the preparation of Bi-based supercon- ductors from the glassy state (3-7); however, attention has