Formula omitted] MAS-NMR and FTIR analyses on the structure of CuO-containing sodium poly- and meta-phosphate glasses

Abstract

Two series of CuO-containing sodium phosphate glasses with 40, and 50mol% P2O5 were prepared. 31P magic angle spinning nuclear magnetic resonance (MAS-NMR) and Fourier-transformed infrared (FTIR) spectra were applied to characterize the short-range structure of the glasses. 31P NMR spectra reveal the presence of Q2- and Q1-tetrahedral sites in both glass series. The depolymerization of phosphate chains by the addition of CuO was described by the decrease in the concentration of Q2-tetrahedral sites and the increase in that of Q1-tetrahedral sites. The presence of 1Q2 peaks (Q2 site covalently bonded to one copper) in the 31P NMR spectra indicates that a portion of CuO, which acts as a network former, enters the glass network to form covalent POCu linkage in the polyphosphate glasses. The 1Q2 site population increases with increasing CuO content. Almost all the CuO act as network modifiers in the metaphosphate glasses with CuO <30mol%; the 1Q2 sites only exist in the glasses with high CuO content (≥30mol%). FTIR analyses reveal the shortening of phosphate chains by the shift of (POP)as band to higher wavenumber due to the addition of CuO. The absorption band of the POCu stretching mode is assigned at around 1080cm−1.