Study on the oxygenation process during the heat treatment of TFA-MOD YBCO thin films by in situ resistance measurement

Highlights: •In situ resistance measurement (ISM) was carried out on MOD-YBCO thin films. •Thermodynamic behaviors of the oxygenation process were studied by using ISM. •A defect reaction was found to control the mechanism of the oxygenation process. •Porosity accelerated diffusion mechanism was proposed for the MOD thin film system. -- Abstract: The oxygen content is one key factor to determine the properties of YBa2Cu3O6+y (YBCO) high temperature superconductors. In this study, YBCO thin films were produced by TFA-MOD method. The oxygenation process was carried out at 450 °C for 40 min, in various oxygen partial pressures from 0.01 to 1 atm. An in situ resistance measurement system was built up to record the resistance evolution during the whole heat treatment process. It was found that the resistance decreased exponentially and reached a saturate value in a few minutes during oxygen annealing. It was also found both the balanced resistance and the c-axis length of YBCO decreased with increasing oxygen partial pressure. A defect reaction was found to control the mechanism of the oxygenation process. A porosity assisted oxygen diffusion mechanism was proposed to explain the fast diffusion kinetics of oxygen in MOD YBCO thin films