Thermal reactivity of YBa2Cu3O7-δ with Al2O3 addition in air atmosphere

The high–temperature thermal reactivity of YBa₂Cu₃O_7-δ (Y123) compound with Al₂O₃ addition (0.5–10?wt%) was investigated and the thermal processes were described. Experimentally obtained results showed that Al₂O₃ firstly reacted with Y123 at temperatures far below the peritectic melting point of Y123. During this solid state reaction Al partially diffused into Y123 and formed a solid solution. Also, the formation of Al-rich complex oxides, mainly with barium, and basic secondary phases as Y₂BaCuO₅ and CuO, was observed with increasing Al₂O₃ content. The formation of additional secondary phases with Al₂O₃ provoked their reactivity with Y123 or between themselves. After increasing the temperature of the powder mixtures above the peritectic melting point of Y123 it was found that Al was incorporated in Y123 at higher concentrations than during the solid state reaction. The reason for that could be a partial or full dissolution of Al-rich complex oxides formed at lower temperatures which in turn increased the source of Al for the incorporation in Y123.The thermal behaviour of powder mixtures was investigated with the help of simultaneous differential thermal analysis and thermogravimetry. Morphology and microstructure were examined using powder X-ray diffraction and scanning electron microscopy in combination with energy dispersive X-ray spectroscopy.