Spectroscopic and chromatographic analyses of zinc borophosphate glasses

Thirteen zinc borophosphate glasses with analysed compositions defined by constant O/P ratios of 3·1, 3·4, and 3·7 were prepared, and their structures characterised by Raman spectroscopy, high pressure liquid chromatography (HPLC), and ¹¹B magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. The ¹¹B MAS NMR spectra show that boron is predominantly incorporated into tetrahedral sites with four phosphate next-nearest neighbours, B(OP)₄, although some of these tetrahedra appear to have another borate unit as a next-nearest neighbour, B(OP)₃(OB)₁. HPLC and Raman spectroscopy show that as the O/P ratio increases, the phosphate anions become progressively smaller because of the formation of B–O–P bridges. The effects of composition on structure are discussed by considering the availability of oxygens on the phosphate anions to coordinate Zn- and B-polyhedra, and these structures are compared to those reported for zinc aluminophosphate glasses.