Precipitation of ZnO in Al2O3-doped zinc borate glass ceramics

Crystallization behavior of the oxide semiconductor ZnO in zinc borate glass was investigated. The precipitated crystalline phase of glass ceramics containing a small amount of Al 2 O 3 was α -Zn 3 B 2 O 6 whereas that of the glass ceramics containing a large amount of Al 2 O 3 was ZnO. It was found that the c -oriented precipitation of ZnO in a glass ceramic was brought about by the in-plane crystal growth of needle-like ZnO crystallites along the a -axis. Amount of Al 2 O 3 that can make glass network affected the coordination state of B 2 O 3 in the glass, and a three-coordinated BO 3 unit was preferentially formed in the glass containing a higher amount of Al 2 O 3 . The present results suggest that crystallization of ZnO from multi-component glass is dominated by the local coordination state of the mother glass.