Characteristics of Hg-Based Superconductors Prepared at 0.2 GPa by Hip

Abstract

The preparation of Hg(Pb)BCCO (1201) and (1223) phases was performed by hot-isostatic-pressing (HIP) using simple oxides as precursors canned in silver tube. In the case of Hg 0.8 Pb 0.2 Ba 2 CuO 4+δ the preparation, carried out at 800 °C and 0.2 GPa for 5 hrs, yielded a single phase bulk sample. On the other hand the preparation of Hg 0.8 Pb 0.2 Ba 2 Ca 2 Cu 3 O 8+δ at 820 °C and 0.2 Gpa for 5 hrs allowed the attainment of a high volume fraction of 1223 phase. Magnetic susceptibility of 1201 phase showed a granular transition around 90 K; in the case of 1223 the value was ≈128 K followed by a broadened intergranular transition. These results show the feasibility of 1201 phase synthesis with high purity and of 1223 phase in large amount (>80%). The possibility to obtain the samples directly in form of dense bulks (with density ≥ 85%) stresses the importance of this technique in relation to the intrinsic low thermal stability of the superconducting phases.