Effect of borate substitution on zinc phosphate glasses

Abstract

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 BO_4/2 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.