Crystallization Exotherms of Zirconia‐Hafnia Mixtures

Abstract

Differential scanning calorimetry was used to study the crystallization behavior of ZrO2‐HfO2 mixtures. The materials prepared by admixing Zr(NO3)4 and Hf(NO3)4 exhibited a peak at 40 wt% Hf composition in the exothermic‐heat‐versus‐mixed‐oxide composition curve. In contrast, the materials prepared by precipitation from a solution prepared from anhydrous HfCl4 and ZrC14 exhibited a gradual decrease in exothermic behavior with increasing Hf content. The temperature for the exotherm increased with increasing Hf content. The data indicate that the exotherm is due to the formation of a crystalline material and not due to a phase transformation.