IR and Raman investigation on the structure of (100-x)B2O3-x[0.5 BaO–0.5 ZnO] glasses

Glasses with molar composition of (100-x)B2O3-x[0.5 BaO–0.5 ZnO], x=40, 50, 60, 70 were prepared from the melts of ZnO, BaCO3 and H3BO3 mixture. The structure and thermal behavior were characterized by IR and Raman spectroscopy, DSC and Dilatometer. The investigation shows that the transition of the structural unit [BO4] (BIV) to [BO3] (BIII) happens when BaO and ZnO content x increases in the borate glass, resulting in fewer BIII–O–BIV bonds and more BIII–O–BIII bonds. At the same time, the diborate groups, which are found to be the predominant structural group of the glass with high B2O3 content, gradually changes into ring-type metaborate, pyro- and orthoborate groups. With increasing ZnO and BaO content x, the glass transition temperature (Tg) and the softening point (Tf) decreases, while linear expansion coefficient (α) increases, that comes from the weakening of the glass network.