Nano-crystallization and highly oriented crystal line patterning of Sm3Â +-doped Bi2GeO5 and Bi4Ge3O12 in bismuth germanate-based glasses

Glasses based on the system of Sm2O3-Bi2O3-GeO2 were prepared, and their electronic polarizabilities and formation behavior of Bi2GeO5 (monoclinic) and Bi4Ge3O12 (cubic) crystals were clarified. The glasses showed large electronic polarizabilities (αO2-(n)) and optical basicities (Λ(n)), e.g., αO2-(n) = 2.783 Å3 and Λ(n) = 1.070 for 50Bi2O3-50GeO2 glass, indicating a basic nature in the glasses. The small addition of Sm2O3 was found to be effective for the control of the crystallization of Bi2O3-GeO2 glasses. Sm3 +-doped Bi2GeO5 nanocrystals with an ellipsoidal shape (a(long) ~ 32 nm b(short) ~ 20 nm) and Sm3 +-doped Bi4Ge3O12 nanocrystals with a spherical shape (~ 7 nm) were formed in the glass-ceramics of 5Sm2O3-45Bi2O3-50GeO2 and 5Sm2O3-31Bi2O3-54GeO2-10B2O3, respectively. Highly oriented crystal lines consisting of Bi2GeO5 or Bi4Ge3O12 were patterned at the glass surface by continuous wave Yb:YVO4 fiber laser (wavelength: 1080 nm) irradiations, suggesting the possibility of the design and control of spatially selected crystallization in Bi2O3-GeO2 based glasses.