Kinetics and mechanism of the solid-state synthesis of fluorite in ZrO₂-Y₂O₃-Ln₂O₃ (Ln=Ce,Nd,Er) systems

Abstract

The mechanisms and kinetics of the solid-state reactionx ZrO₂+yY₂O₃+(1−x−y) Ln₂O₂→ ternary fluorite solid solution was studied in the temperature range 1350 to 1650° C by quantitative X-ray diffraction analysis. In the ZrO₂-Y₂O₃-CeO₂ system the fluorite formation process starts with the simultaneous interaction of CeO₂ and Y₂O₃ with ZrO₂, although the reaction rate of ceria with zirconia is more rapid. In the ZrO₂-Y₂O₃-Nd₂O₃ system, the formation of a pyrochlore, Nd₂Zr₂O₇, responsible for the formation process of the ternary fluorite solid solution. Finally, in the ZrO₂-Y₂O₃-Er₂O₃ system, a competitive interaction of yttria and erbia occurred in the formation process of the ternary solid solution. The kinetic data were treated using the Avrami equation, and activation energies for the processes studied calculated.