Some Further Studies in Combustion Synthesis of the YBa₂Cu₃0_7–x Superconductor

Abstract

The combustion synthesis of the YBa₂Cu₃O_z–x ceramic superconductor was achieved from CuBaO₂ and Y₂O₃ mixtures, using both self-propagating high-temperature synthesis (SHS) and thermal explosion modes. Particular attention was paid to establishing the mechanism of formation of the YBa₂Cu₃O_3–2 product. Previous studies included effects of BaO₂ and Cu particle sizes, along with quenching of reacting pellets. It was shown that the mixture of reactants undergoes a complex sequence of reactions before eventually forming the final product. In the present work, the effect of the Y₂O₃ particle size has been investigated. The initiation of YBa₂Cu₃O_7–x formation has also been studied by providing a portion of the copper as either Cu₂O or CuO. It is shown that the oxidation of Cu to form Cu₂O is a necessary step for the reaction to become self-sustaining, but that excessive oxidation to Cu₂O inhibits the reaction, leading to partially reacted pellets.

Key words:

• Synthesis of Y123
• combination
• synthesis mechanism