On the kinetics of superconducting phase formation in Y 1Ba 2Cu 3O y

Abstract

The high-temperature superconductor Y 1Ba 2Cu 3O y was investigated by in situ X-ray diffraction experiments at high temperatures and by differential scanning calorimetry under various partial pressures of oxygen, by thermogravimetrical analysis, and by resistivity measurements. As-prepared and oxygen-deficient samples were annealed under various oxygen atmospheres at constant oxygen partial pressures and/or constant temperatures below 800 °C. The smallest oxygen partial pressure necessary for orthorhombic phase formation was measured at various temperatures and the kinetics of the tetragonal-to-orthorhombic transition was studied. A diffusion constant of oxygen in the “123” compound at 400 °C of about 1 × 10 − 11 cm 2s − 1 and an activation energy of diffusion of about 1.6 eV was determined.