Behavior of indium oxide in zinc phosphate and borophosphate glasses

The effect of indium oxide on the structure and properties of zinc phosphate and zinc borophosphate glasses has been investigated in the series (50−x)ZnO–xIn2O3–50P2O5 and 30ZnO–(20−x)B2O3–xIn2O3–50P2O5 with x = 0–20 mol% In2O3 in both series. Their physical properties were measured, and their structure was studied by Raman and NMR spectroscopy. Glass transition temperature in the phosphate glass series increases with increasing In2O3 content as well as their chemical durability. The observed changes in the 31P MAS NMR spectra with increasing In2O3 content revealed the depolymerization of phosphate chains due to the replacement of ZnO by In2O3 resulting in an increase in the O/P ratio in the glass structure. 11B MAS NMR spectra revealed the presence of BO4 units in the glass structure in the borophosphate glass series; these spectra give no evidence for the formation of B–O–In bonds. Their glass transition temperature slightly decreases with increasing In2O3 content. The values of the molar volume in these glasses do not change substantially when B2O3 is replaced by In2O3. This can be ascribed not only to differences in boron (BO4) and indium (InO6) coordination, but also to a higher ionicity of In···O bonds in comparison with B–O bonds. The obtained data resulted in the conclusion that indium oxide behaves as a modifying oxide in both glasses.