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 Al₂O₃ was α-Zn ₃B₂O₆ whereas that of the glass ceramics containing a large amount of Al₂O₃ 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 Al₂O₃ that can make glass network affected the coordination state of B₂O₃ in the glass, and a three-coordinated BO₃ unit was preferentially formed in the glass containing a higher amount of Al₂O₃. The present results suggest that crystallization of ZnO from multi-component glass is dominated by the local coordination state of the mother glass.