Up to date, oxygen controlled melt grown (OCMG) mixed rare earth REBa₂Cu₃O_y (RE: NEG, NSG, SEG, etc.,) system showed a considerable improvement in critical current density (J_c) and irreversibility field (H_irr) values at 77K. The combination of mixed rare earth is particularly challenging, as it is difficult to regulate the formation of matrix and secondary phases. In this study, we primarily focused on optimizing the composition of Gd, Y and Er ratio for superior properties. We started with exploring bulk (Gd_0.33,Y_0.33-X,Er_0.33+X)Ba₂Cu₃O_y superconductor with varying Er content, where x is 0-0.2 in 0.05 interval. DTA results are used to optimize the heat pattern. Single grain bulk of diameter 20 mm are fabricated by IG process in air. The best bulk (Gd_0.33,Y_0.13,Er_0.53)Ba₂Cu₃O_y exhibited a trapped field of 0.53 T at 77 K, and critical current density at self-field of 238 kA/cm² and 63 kA/cm² (H//c-axis) at 50 and 77 K respectively. Microstructural analysis revealed secondary phases (Gd,Y,Er)₂BaCuO₅ with various sizes. EDX analysis conformed that larger 211 secondary phase particles are comprised of combinations of Gd, Y, and Er elements, while the smaller ones are Er-rich. Improved critical current density and trapped field values with increasing Er content are explained based on the microstructural features.

Keywords: mixed rare earth, (Gd,Y,Er)Ba2Cu3Oy, IG