Correlation between Surface-Crystallized ZnO and the Amount of Al2O3 in Borate-Based Glass-Ceramics

The correlation between the Al2O3 content and the crystallization behavior of the oxide semiconductor ZnO in 5CaO-25B(2)O(3)-45ZnO-xAl(2)O(3)-10K(2)O-15SiO(2) (CaBZAKSx) glass-ceramics was investigated, with a particular focus on the c-oriented crystallization behavior of ZnO. C-oriented precipitation of ZnO crystallites in glass-ceramics is brought about by the in-plane crystal growth of ZnO along the a-axis. Addition of Al2O3 promotes the formation of ZnO4 rather than ZnO6 in the mother glass, and the ZnO4 unit affects the nucleation and selective crystallization of ZnO that also takes the four-coordination state of Zn. The present results suggest that crystallization of ZnO from multi-component glass is also dominated by the local coordination state of the mother glass.