Reaction Kinetics in the Superconducting YBa2Cu3O7-x and SmBa2Cu3O7-x

The compounds under investigation were prepared with nominal composition MBa2Cu3O7-x , M being Y or Sm, through solid state reaction starting from Y2O3 , Sm2O3, BaCO3 and CuO powders. Reaction were investigated by thermogravimetric and differential thermal analysis in the temperature range 900 - 980 °C. Reaction kinetics of MBa2Cu3O7-x solid state synthesis were evaluated according to the mathematical relationships theoretically derived for phenomenological models. In the Y-based system the phase boundary model provides a reaction kinetics suitable to describe the process, while a three dimensional diffusion model fits the data in the Sm-based system . The influence of the mixing method on the reaction kinetics was evaluated. Microstructuralfeatures of superconducting samples were analyzed.