Application of hot isostatic pressing in the synthesis of hg-based superconductors

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 Hgo.gPbo.2Ba2CuO4+s the preparation, carried out at 800 °C and 0.15 GPa for 5 hrs, yielded a single phase bulk sample. On the other hand the preparation of Hg0.,Pbo.zBa2Ca2Cu3O8+5 at 820 °C and 0.15 GPa for 5 hrs allowed the attainment of a high volume fraction of 1223 phase. Magnetic susceptibility of 1201 phase showed an intragranular 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.