Survival of Fragmented BO 4 Units in Highly Modified Rare-Earth-Rich Borate Glasses

Highly modified La O -Y O -B O ternary glasses were fabricated by using a levitation technique. The thermal and structural properties of (50 - )La O - Y O -50B O glasses and (60 - )La O - Y O -40B O glasses were investigated. Raman scattering spectra indicated that B atoms mainly formed isolated planar BO triangles similar to those of crystalline LaBO . This process was independent of the ratio of La O and Y O . B magic angle spinning nuclear magnetic resonance spectra confirmed that the BO units that should have disappeared in the glass with highly modified compositions remained as fragmented species. Approximately 4% of the B atoms formed BO in the 50La O -50B O glass. This ratio increased with an increase in the Y O content, and it reached its maximum value (15%) in the 50Y O -50B O glass. Comparison of the electron density distribution was conducted using calculations of the LaBO and YBO crystals and indicated that more electrons localize near the atomic nuclei in the Y-O bond than in the La-O bonds. Comparison of the electron density distribution was conducted using calculations of the LaBO and YBO crystals and indicated that electrons in the Y-O bond localize near the atomic nuclei compared to those in the La-O bonds. Thus, the unconventional existence of BO in a highly modified glass is attributed to the increase in the level of Y , which causes the localization of electrons near the atomic nuclei. Thus, the ratio of BO and BO in highly modified glass can be controlled by tuning the glass content of modifier rare-earth oxides, which opens a new door to glass science.