EFFECT OF MN INCLUSION IN SUPERCONDUCTING YBCO-BASED COMPOSITES

The doping effect of Mn in polycrystalline YBa2Cu3O7-delta material (Y BCO) is carefully analyzed considering the transport properties of com posites formed by small inclusion particles of Mn embedded whether in a YBCO matrix or in superconducting Fe-YBCO composites. In both cases, the improvement of their respective electrical resistivity was eviden ced. The use of double element doping clearly shows that an a priori d egradation of the YBCO electrical properties by Fe atoms can be greatl y restored by appropriate Mn doping. This character can be very useful for technological applications. This improvement is mainly due to the reduction of the secondary and/or insulating phases formed at the gra in boundaries, limiting the current transport. The involved mechanism is the probable existence of free charged Mn-based species which are r esponsible for an optimal oxygenation in the material contributing to the electrical response improvement. These species can be located in t he composite, whether entering the CuO chains of the YBCO lattice or c omplexing and reducing the secondary phases formed during the sinterin g process, especially Fe2O3 and Y2BaCuO5 in the case of Fe-YBCO compos ites.