Phase relations in the aluminothermic reduction of ZrO2

Abstract

This paper presents thermodynamic evaluation of reactions between ZrO2 and aluminum, which indicates that the aluminothermic reduction of zirconium oxides at temperatures above 600°C is only possible when Al x Zr y intermetallic compounds form in the metallic phase. Thermodynamic analysis results are supported by experimental data, which demonstrate that, at ZrO2: Al ratios in the range 0.4–1.4, the aluminothermic reduction of ZrO2 leads predominantly to the formation of the congruently melting compounds Al2Zr and Al3Zr. The phase formation in the slag yields various forms of calcium aluminates and calcium zirconates and leads to a gradual reduction in the oxidation state of the zirconium.