Thermal degradation of poly(acrylic acid) containing metal nitrates and the formation of YBa2CU3O7-x

The use of polymers containing metal salts as ceramic high-temperature superconductor (HTSC) precursors may provide a relatively simple and rapid method for producing materials that can take advantage of advanced polymer processing and then be pyrolyzed to HTSCs. The mechanisms of thermal degradation in these precursors, which have not been characterized, can be used to optimize the pyrolysis conditions for HTSC production. This article describes the degradation of a precursor based on poly (acrylic acid) (PAAc) containing yttrium, barium, and copper nitrates in the proportions needed for the formation of the HTSC YBa2Cu3O7-x (YBCO). This article also describes the effects of the pyrolysis process on the resulting materials. The degradation of the precursor is a complex, multistage process. The presence of the metal ions and HNO3 reduces the thermal stability of PAAc and increases the degradation rate. The results indicate that the initial stages of the pyrolysis should be conducted in argon or nitrogen to inhibit BaCO3 formation and that the final stages should be conducted in air/oxygen to enhance oxidation. Optimization of the pyrolysis conditions produces a YBCO film with minimal contamination. (c) 2005 Wiley Periodicals, Inc.