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

Abstract

The effect of HfO 2 addition on the crystallization behavior of ZnO-Al 2 O 3 -SiO 2 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 HfO 2 . The crystallization peak temperature also decreased by nucleation heat treatments (NHT), and the difference of T C among samples depending on HfO 2 content became less with the increase of NHT time. It was found that HfO 2 works as a nucleation agent because the addition of HfO 2 suppressed the precipitation of SiO 2 by promoting the precipitation of Gahnite(ZnAl 2 O 4 ). The effect of HfO 2 on nucleation is less than TiO 2 or ZrO 2 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 HfO 2 .Key words: