Structural studies of AgPO3–MoO3 glasses using solid state NMR and vibrational spectroscopies

Vitreous samples (1-x) AgPO3–x MoO3 (0 ≤ x ≤ 0.5) were prepared by conventional melt-quenching and characterized by Differential Scanning Calorimetry (DSC). The structural evolution of the vitreous network was monitored by 31P solid state nuclear magnetic resonance and Raman scattering, and assignments were aided by corresponding studies on the model compound AgMoO2PO4. The 31P MAS-NMR data differentiate between species having two, one, and zero P―O―P linkages (Q(2) Q(1), and Q(0) species), respectively. Interatomic connectivities involving these units are revealed by two-dimensional INADEQUATE data, utilizing the formation of double quantum coherences mediated by indirect 31P–31P spin–spin interactions via P―O―P linkages. As this method discriminates against isolated P atoms, it also serves as an important spectral editing tool for constraining lineshape fits. 95Mo NMR data and Raman spectra suggest that the Mo species are most likely six-coordinate, forming four P―O―Mo linkages and are otherwise invariant with composition, except at MoO3 contents ≥ 40 mole %, where some Mo―O―Mo bonding and/or clustering is observed.

► Use of INADEQUATE solid state NMR for spectral editing in glasses.
► New insight on Mo coordination in phosphate glasses.
► Quantitative structural model for AgPO3–MoO3 glass.