I need to know what the role of ZnO and BaO is in the BaO-ZnO-TeO2 glass as paper that I have attached. I could not really understand about the glass composition. Why does the researcher fix the value of ZnO and add varies BaO content ? What the role does ZnO and BaO play in the glass system?
http://www.sciencedirect.com/science/article/pii/S0022309312000051