RAMAN-SPECTROSCOPIC STUDIES OF BAO-GA2O3-GEO2 GLASSES

Raman spectra were collected for barium gallogermanate glasses along t wo compositional joins to determine relationships among glass structur e, chemistry, and physical property variations. As GeO2 content decrea ses for both glass series, the mid-frequency envelope shifts to higher frequencies while the high-frequency features increase in intensity a nd shift to lower frequencies. These trends in the Raman spectra paral lel those reported for binary Li, Na and K germanate glasses, and are interpreted in terms of a reduction in average ring size, as well as a n average lengthening of T-O bonds. The more extreme trends for the mo st barium-rich glasses indicate partial depolymerization of the tetrah edral network and a concomitant increase in the number of non-bridging oxygens. There is no evidence for octahedral Ge or Ga in any of the b arium gallogermanate glasses investigated in this study. The findings determined from the Raman data are consistent with earlier conclusions drawn from Ge and Ga X-ray absorption spectra.