Effect of borate substitution on zinc phosphate glasses

The combination of glass-forming oxides can induce phase separation at the atomistic level, particularly when a mixture involves both ionic and covalent bonds. In this study, we report physical properties of B2O3-substituted ZnO–P2O5 (ZP) glass and the substitution effect of B2O3 on the structure of ZP glasses via magic angle spinning nuclear magnetic resonance (MAS NMR), X-ray diffraction, small angle X-ray scattering, positron annihilation spectroscopy and inelastic light scattering measurements. The 11B and 31P MAS NMR results suggest that the coordination states of boron are affected by the number of bridging oxygen atoms in the substituted PO4 chain structure of the ZP glass. At 5 mol % or less B2O3 substitution, an emerging of atomistic phase separation is not confirmed. On the contrary, at 10 mol % B2O3 substitution, three-coordinated boron formation is confirmed in 11B MAS NMR in addition to a correlation between the BO4/2 units. The substitution of a large amount of B2O3 confirmed the local coordination change of zinc cations in addition to the formation of a cluster-like structure in the low-Q region via small angle X-ray scattering.