Fabrication of surface crystallized glasses with α-Zn3B2O6 and their optical property

Surface crystallization of metastable α-Zn3B2O6 was observed in ZnO-B2O3-CaO-K2O-Al2O3 glass after conventional heat treatment. Precipitation of α-Zn3B2O6 with high orientation degree in the transparent glass–ceramics was confirmed by XRD measurement. Transmission electron microscope image showed that crystalline rods of α-Zn3B2O6 were precipitated from the surface of the glass–ceramics with the crystalline orientation of (1 − 2 1) direction. Although the strongly oriented phase was observed in the glass–ceramics, the polarization direction was not strong from the crystal that can bring strong second harmonic generation (SHG). SHG measurement using a powder sample showed that the 2nd optical nonlinearity of α-Zn3B2O6 glass–ceramics was comparable to that of α-SiO2.