Structure and disorder of phosphates in ${\mathrm{Ag}}_2$O-AgI-${\mathrm{P}}_2$${\mathrm{O}}_5$ glasses

We directly probe the microstructure of the different phosphates in several glasses in the ${\mathrm{Ag}}_2$O-AgI-${\mathrm{P}}_2$ ${\mathrm{O}}_5$ system, by means of variable angle correlation NMR spectroscopy. This two-dimensional experiment separates the chemical-shift powder patterns of the phosphorus sites according to their isotropic chemical shifts. We have thus determined all chemical-shift tensor elements for each chemically distinct phosphorus site in these glasses, and their variation within each site. Our results yield a precise description of the phosphate types and geometries in these glasses.