Gel stabilization in chelate sol–gel preparation of Bi-2223 superconductors Original Research Article

A chelating sol–gel method was used for the preparation of the superconducting Bi-2223 phase. We compared pH range of both solution and gel stability in samples with EDTA, TEA and their equimolar mixture addition. A pH range of stability (for precipitation) was extended in EDTA solutions with addition of TEA. IR spectroscopy was used to identify the type of bonding between EDTA and TEA in a stabilized solution. IR bands belonging to polyester bonding were found in the IR spectra of gels prepared at 130 °C. We describe the influence of both gel decomposition and calcinations regime on the evolution of Bi-2223 phase. The optimized temperature treatment was used for the comparison of superconducting transport and of magnetic properties of the prepared samples. Moreover, an extra 800 °C calcination step was tested to enhance the decomposition of unfavorably formed carbonates.