Optimization of YbBa₂Cu₃O_y Thick Film Formation on MgO Substrates

We optimized the formation process of the YbBa₂Cu₃O_y superconducting thick film prepared from the mixture of Yb₂BaO₄, BaCuO₂, and CuO. Thick films of this composite were sintered at various temperatures between 800 °C and 1025 °C and held for 10 minutes in air, then rapidly quenched in liquid nitrogen. The samples were characterized by XRD, SEM, and magnetization measurements. The XRD analysis indicated that the Yb-123 phase started to form above 800 °C, with optimum at 825 °C. At even higher temperatures (900 °C and 975 °C) the secondary phase and liquid phase predominantly formed. Based on these results, we fabricated good quality YbBa₂Cu₃O_y thick films on an MgO substrate utilizing a double step heating process. According to XRD measurements the Yb-123 films were c-axis oriented, with T_c (onset) 87 K, and high critical current density around 24 kA/cm² at 77 K, H//c-axis. The Yb-123 superconducting thick films on the MgO substrates are considered as the first step to the production of silver sheathed tapes, an advanced analogue to the Bi-2223 system.