Microstructure and trapped field of Al-doped GdBCO–Ag bulk superconductors

The effect of Gd2Ba6Al4O15 powder addition on microstructure, field trapping capability and critical transition temperature, Tc, of GdBCO‐Ag superconductors grown in air is reported. Single-grain GdBCO‐Ag bulk superconductors with different amounts of Gd2Ba6Al4O15 powder were fabricated by the top seeded melt growth process. Addition of 0.3 wt% Gd2Ba6Al4O15 powder increased the maximum trapped field value, BZ max. Microstructure analysis confirmed that, up to 1.0 wt% addition of this powder, Al-based phase is not formed and Al is supposed to substitute Cu in the GdBa2Cu3O7 matrix. Addition of 2.0 wt% Gd2Ba6Al4O15 powder leads to formation of Pt, Al-based phase, which indicates that the solubility limit of Al in the studied system was exceeded. The critical transition temperature, Tc, decreases monotonically with increasing Gd2Ba6Al4O15 powder addition. (Some figures may appear in colour only in the online journal)