REBa₂Cu₃O_7-δ (REBCO/RE123, RE = rare earth elements) superconductors have a wide range of applications due to their high superconducting transition temperature (T_c) of ~92 K and excellent field trapping capabilities. This is very important for developing next-generation high-magnetic field applications, which depends on the magnitude of critical current density (J_c) and how well the magnetic flux motion due to the Lorentz force is suppressed. This can be achieved by dispersing pins such as RE₂BaCuO₅ (RE211) particles or other nanometer-sized defects in the superconducting RE123 matrix. Recently, we have demonstrated that high-energy ultrasound irradiation effectively controls the initial RE211 (RE211_Ultra) particle size. By employing the RE211_Ultra particles, the J_c and trapped fields of various REBCO single-grain bulk superconductors were improved.

In this study, for improving the 123-matrix pinning, (Y_1-x, Gd_x)Ba₂Cu₃O_7-d (YGdBCO) superconductors were synthesized via top-seeded melt growth method by the addition of 20 mol% of ultrasonically pre-treated (with 450 W for 30 min) Gd211 particles. Systematic isothermal experiments were conducted at various constant temperatures (from 1020 ^oC – 990 ^oC) indicating that a safe growth window for fabricating large YGdBCO bulk single grains is 1015 ^oC – 990 ^oC. The microstructural and composition studies (mapping, line scan and point scans) performed via electron microscopy and energy dispersive spectroscopy on YGdBCO samples indicated that the inclusion of the Y211 phases wrapped in Gd211 particles. All YGdBCO samples exhibited superconductivity above 92.5 K. A maximum of 74.1 kA/cm² at 77 K and self-field was achieved in the YGdBCO sample grown at 1000 ^oC. Further, we will outline the relation of the developed microstructure and superconducting properties dependence on the isothermal growth temperature.

Keywords: (Y, Gd)Ba2Cu3O7-𝛅, single-grain, ultra sonication, microstructure