Effect of Firing Temperature on Microstructure and Superconductivity of YBCO Films Derived from Low-fluorine Solution

摘要

Using a low-fluorine solution, YBa_2Cu_3O_(7-x) (YBCO) superconducting films were prepared on LaAlO_3 (LAO) substrates by dip-coating method. YBCO films were fired at different temperatures with same oxygen pressure of 1.3 vol% and water vapor pressure of 7.4 vol%. Effect of firing temperature on film microstructure and superconductivity was investigated. The results indicated that YBCO films with high-degree c-axis orientation (the degree of c-axis orientation reached 96%) can be obtained when heat treated at 800 ℃. At this temperature YBCO films were grown on LAO with cubic-on-cubic mode, resulting in a high critical transition temperature (71) of 91.5 K, and critical current density (J_c) of lager than 1 MA/cm~2. However, when fired at lower temperatures, YBCO films trended to form α-axis grains, which degraded J_c of films. And a higher heat treatment temperature also depressed superconductivity of YBCO films.