TEM analysis for crystal structure of metastable BiBO3 (II) phase formed in glass by laser-induced crystallization

The crystal structure of metastable BiBO3 (II) phase was investigated using transmission electron microscope (TEM) observations combined with a focused ion beam (FIB) sample preparation and simulation technique. A highly oriented crystal line on the glass surface with BiBO3 was obtained using Yb:YVO4 laser irradiation (λ = 1080 nm) in a glass with the composition of 5Sm2O3-5Gd2O3-35Bi2O3-55B2O3. The crystal line was sliced into thin foils using FIB from three mutually perpendicular directions, and electron diffraction patterns were obtained by TEM observations for the thin foils. The crystal structure of rare-earth-doped BiBO3 (II) was successfully determined as the noncentrosymmetric monoclinic space group C2 or Cm with the lattice constants of a = 6.634 Å, b = 4.979 Å, c = 6.443 Å, and β = 143.4°, which parameters reproduce well X-ray diffraction patterns for BiBO3 (II) phase formed in the crystallization of the glass. The structure and a model of crystal growth of BiBO3 (II) in the crystal line patterned by the laser-induced crystallization were proposed.