Preparation of GdBa ₂ Cu ₃ O _6+x (GdBCO) precursor powder by spray‐drying a nitrate solution containing PEG

Abstract Several precursor powders, obtained after precipitation from metal nitrate solution containing polyethylene glycol (PEG) (inside a Pyrex glass reactor or by spray‐drying), and their thermal evolution to GdBa ₂ Cu ₃ O _6+x (GdBCO) were analyzed by thermogravimetry, differential thermal analysis, Fourier‐transform infrared spectroscopy, and X‐ray diffraction. The amount of PEG had a crucial role in the BaCO ₃ content of the “Kjeldahl precursors,” but a minor effect on the degree of transformation to GdBCO at 900°C, which did not reach completion after 1 hour. In contrast, a low‐PEG spray‐dried powder led to almost 100% GdBCO in only 5 minutes. The high degree of cation dispersion reached by spray‐drying and the coexistence with a liquid phase can explain this short reaction time. The spray‐dried powder compares favorably with the mechanical mix of metal oxides and Ba carbonate that is commonly used as precursor powder for the synthesis following a solid‐state reaction.