LOW-FREQUENCY RAMAN-SPECTRA OF BARIUM BORATE GLASSES IN THE SYSTEM (BACL2)Y[(BAO)X(B2O3)1-Y-X]1-Y FOR VARIOUS X AND Y

Low frequency Raman spectra of glasses of the types (BaO)x.(B2O3)1-x a nd (BaCl2)y . [(BaO)x . (B2O3)1-y-x]1-y have been reported. The temper ature reduced Raman spectra show peaks at 67, 116 and 140 cm-1 for the binary glass. The bands at 116 and 140 cm-1 are ascribed to the libra tional motions of the borate groups and the 67 cm-1 band arises becaus e of the limited structural correlation range (SCR) of the glass netwo rk, causing a maximum of the frequency dependent Raman coupling coeffi cient. Due to addition of BaO in upsilon-B2O3, the oxygens are mostly incorporated in the formation of BO4 units; however large Ba2+ ions al so enhance the number of non-bridging oxygens at higher concentrations of dopant. These barium ions as well as chlorine ions are accomodated in the interstitial vacancies of the glass network which leads to an expansion of the network structure.