Critical current density and microwave surface resistance of 5-cm-diameter YBCO films on LaAlO3 substrates prepared by MOD using an infrared image furnace

Inductive critical current density (Jc) and microwave surface resistance (Rs) were investigated for 0.7-μm-thick epitaxial YBa2Cu3O7−y (YBCO) films on 5-cm-diameter LaAlO3 substrates prepared by a chemical solution-based metal organic deposition (MOD) process using an infrared image furnace. By varying the heating rate at ramp during the final heat treatment, we obtained various orientations of YBCO; the c- and a-axis orientation at a slower rate, i.e., 20-100 °C/min while the pure c-axis orientation at a faster rate, 200 °C/min. The c-axis-oriented YBCO films showed excellent superconducting properties; for example, a high inductive-Jc (77 K) of 2.6 MA/cm2 and low Rs (12 GHz)'s of 0.24 and 0.52 mΩ at 50 and 77 K, respectively, by a sapphire rod resonator method. The c- and a-axis-oriented films exhibited a lower Jc and a higher Rs. It was found that the Jc and Rs values of MOD-derived YBCO films showed a strong correlation; approximately, Rs is inversely proportional to Jc. This correlation is in good agreement with a previous report by Ohshima et al. for sputtered-YBCO films on BaSnO3-buffered MgO substrates.