Structural changes during the crystallization of the Bi4Ge3O12 glasses

Abstract Bismuth–germanate glass ceramics with the composition 40% Bi 2 O 3 –60% GeO 2 (in molar percents) were prepared through controlled crystallization of melt-quenched glass. The Raman and FTIR spectra recorded in the as-made glasses show broad bands at 240, 400, 780 cm − 1 and 400, 745 cm − 1 have been assigned Ge–O bonds which appear right after preparation. X-ray diffraction has shown that the as-made glasses are amorphous, but after annealing above the crystallization temperature at 558 °C, BGO nano-crystallites with a size of about 50 nm precipitate in the glass matrix. The Raman and FTIR spectra reveal sharp peaks associated to the “internal” and “external vibrations” of GeO 4 tetrahedral groups inside the BGO nano-crystallites. In the glass ceramic sample the transparency region is shifted at longer wavelengths compared to as-made glass, due to the Rayleigh scattering on the BGO nano-crystallites.