Network connectivity in cesium borosilicate glasses: 17O multiple-quantum MAS and double-resonance NMR

► 17O NMR results imply a non-negligible degree of heterogeneity in a cesium borosilicate glass. ► Cesium volatilization shifts the melt composition toward the liquid-liquid immiscibility region, favoring phase separation. ► Dipolar-recoupling NMR directly determines bridging oxygen peak assignments and confirms the insensitivity of key NMR parameters to modifier identity.