Synthesis of a metal oxide by forming solvate eutectic mixtures and study of their synthetic performance under hyper- and hypo-eutectic conditions

The synthesis of YBa2Cu3O7-x (YBCO or 123) superconductor was carried out under hyper- and hypo-eutectic conditions with different ammonium compounds, i.e. ammonium nitrate, formate, acetate, carbonate, bicarbonate, and tetramethylammonium nitrate. The aim was to find more affordable synthetic pathways using highly available and cheaper compounds, as well as to study the crystal formation under no-carbon conditions when ammonium nitrate was employed. Best results were obtained when eutectic conditions were achieved, namely by ammonium nitrate and the metal nitrates in a 5:1 molar ratio (81 % of the superconductor). Ammonium formate, acetate, carbonate, and bicarbonate did not produce eutectic mixes. Temperature analysis of the reaction carried out by ammonium nitrate/metal nitrates indicated the formation of barium carbonate, despite no carbon source is used in this reaction, this phenomenon is further discussed in this work. Consequently, tetramethylammonium nitrate, as chelator and carbon source, was used, providing > 96 % of the superconductor.