Ceramic Tl-oxide based superconductors reinvestigated by magnetic separation technique and SQUID measurements

• Published in: Solid state sciences 2011-10, Vol.13 (10), p.1879-1884
• Main Authors: Mogare, K.M., Landau, I., Guérin, N., Trusch, B., Wagner, M., Locherer, T., Jansen, M., Hulliger, J.
• Format: Article
• Language: English
• Subjects: Bulk sampling; Ceramics; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Grains; Magnetic properties; Magnetic separation; Onset of superconducting diamagnetism; Physics; Properties of type I and type II superconductors; SQUID; SQUIDs; Superconducting particles; Superconducting quantum interference devices; Superconductivity; Superconductors; Tl-1223; Tl-2223
• ISSN: 1293-2558; 1873-3085
• DOI: 10.1016/j.solidstatesciences.2011.07.023

Ceramic samples of Tl 2Ba 2Ca 2Cu 3O 10 (Tl-2223) and TlBa 2Ca 2Cu 3O 9 (Tl-1223) superconductor were resynthesized by using several preparation procedures and investigated by means of magnetic separation technique, allowing evaluation of the superconducting critical temperature of individual grains as small as 25 μm. Although an onset of diamagnetism detected by SQUID measurements was observed around 130 K in Tl-2223 and 134 K in Tl-1223, no grains with T c  > 125 K were found for Tl-2223 and with T c  > 130 K for Tl-1223. Furthermore, the volume fraction of superconductivity of such ceramics was less than 5% and 3% in best samples of Tl-2223 and Tl-1223, respectively. Here we provide a detailed comparison of results obtained by magnetic separation technique with those by SQUID applied to individual grains and bulk samples. [Display omitted] ► Magnetic separation technique for the investigation of ceramic powder samples. ► Reinvestigation of Tl-oxide-cuprate superconductors. ► Investigation of onset of diamagnetism by a scaling method. ► Comparison of single grain diamagnetism measured by SQUID and magnetic separation.