Factors controlling carbon retention in YBa2Cu3O7−δ

Abstract

Natural degradation of YBa2Cu3O7−δ powders leads to trapping of CO2 by the powder. The presence of residual carbon in ceramics or textured materials can strongly affect the superconducting properties. Optimal conditions for carbon elimination during thermal treatment are defined. Amounts of carbon lower than 500 ppm are easily obtained when thermal treatment is performed in temperature, gas flowing rate, and heating ramp conditions allowing CO2 departure before pore closure. Liquid phase formation and the presence of BaCuO2 are limiting factors. An oxycarbonate formed by reaction between this latter compound and evolved CO2 is implied in the last step of the decarbonation process.