Effect of HfO₂ addition on nucleation in ZnO-Al₂O₃-SiO₂ glass

Abstract

The effect of HfO₂ addition on the crystallization behavior of ZnO-Al₂O₃-SiO₂ glasses, which shows volume crystallization, was studied. The crystallization peak temperature　(T_C) obtained by DTA for as cast glasses decreased with the addition of HfO₂. The crystallization peak temperature also decreased by nucleation heat treatments (NHT), and the difference of T_C among samples depending on HfO₂ content became less with the increase of NHT time. It was found that HfO₂ works as a nucleation agent because the addition of HfO₂ suppressed the precipitation of SiO₂ by promoting the precipitation of Gahnite(ZnAl₂O₄). The effect of HfO₂ on nucleation is less than TiO₂ or ZrO₂ which are known well as nucleation agents. The low diffusion rate of Hf due to its heavier atomic weight than Ti and Zr　would be a reason for the low nucleation ability of HfO₂.