Thermodynamic model of ZnO-Nb2O5-P2O5 glasses - parameterization and validation

On the basis of experimental structural data ten system components were considered in the ZnO-Nb2O5-P2O5 thermodynamic model of Shakhmatkin and Vedishcheva - ZnO, Nb2O5, P2O5, ZnP4O11, Zn(PO3)(2), Zn2P2O7, Zn-3(PO4)(2), NbO(PO3)(3), (NbO)(4)(P2O(7))(3), and NbOPO4. The molar Gibbs energies of ZnO, Nb2O5, P2O5, and Zn-3(PO4)(2) were taken from the FACT database. The unknown Gibbs energies of the other components were estimated by minimizing the sum of squares of deviations between the calculated and measured equilibrium molar amounts of system components for the series xNb(2)O(5)center dot 50ZnO center dot(50-x)P2O5. The model was validated by the Multivariate Curve Resolution (MCR) and Malfait's analysis of Raman spectra of xNb(2)O(5)center dot(50-x)ZnO center dot 50P(2)O(5) glasses. The MCR analysis performed for three components resulted in loadings that were in acceptable coincidence with partial Raman spectra obtained by Malfait's decomposition. Both the MCR and the Malfait's decomposition reproduced the experimental Raman spectra very well - on the level of experimental error.