Optimization of YbBa2Cu3Oy Thick Film Formation on MgO Substrates

We optimized the formation process of the YbBa2Cu3Oy 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 YbBa2Cu3Oy 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 Tc (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.