The structure and certain properties of CaO-In2O3-P2O5 glasses

The structure of bulk glasses of xIn2O3-(50-x)CaO-50P2O5 system was studied. A structural model was proposed based on a detailed analysis of both Raman and 31P MAS NMR spectra and along with the results of an X-ray analysis. This model is based on the idea of chemical compounds as components having the lowest Gibbs energy and being therefore the most stable. Chemical compounds used by the model: Ca(PO3)2, Ca2P2O7, In(PO3)3, In4(P2O7)3, CaIn2(P2O7)2 and InPO4 were proposed on a common basis of the chemical composition and the experimental results. The model demonstrates that the equilibria in the glass-forming melts maintains a mean coordination of cations of practically four across the entire range of the glass-forming region, and that with an increasing concentration of indium, the number of MeOP bonds increases by a quarter almost linearly. The validity of the model was verified by experimentally obtained compositional dependencies density, molar volume, glass transition temperature and thermal expansion coefficient.