Solid State NMR: A Powerful Tool for the Characterization of Borophosphate Glasses

This review will show how solid state nuclear magnetic resonance (NMR) has contributed to a better understanding of the borophosphate glass structure. Over the last fifteen years, 1D and 2D magic angle spinning (MAS)-NMR has been used to produce key information about both local and medium range organization in this type of glass. After a brief presentation on borophosphate glasses, the paper will focus on the description of the local order of phosphate and borate species obtained by 1D ³¹P-and ¹¹B-MAS-NMR experiments, with a special emphasis on the improvements obtained at high magnetic fields on the borate speciation description. The last part of this review will show how correlation NMR provided new insights into the intermediate length scale order. Special attention will be paid to the quantitative data retrieved from ¹¹B/³¹P REDOR-based NMR sequences and to the qualitative connectivity schemes observed on the 2D ¹¹B/³¹P maps edited with the heteronuclear multiple quantum coherence (HMQC) NMR techniques.