31P MAS-NMR and FTIR analyses on the structure of CuO-containing sodium poly- and meta-phosphate glasses

Two series of CuO-containing sodium phosphate glasses with 40, and 50 mol% P2O5 were prepared. P-31 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. P-31 NMR spectra reveal the presence of Q(2)- and Q(1)-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 Q(2)-tetrahedral sites and the increase in that of Q(1)-tetrahedral sites. The presence of (1)Q(2) peaks (Q(2) site covalently bonded to one copper) in the P-31 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 (1)Q(2) site population increases with increasing CuO content. Almost all the CuO act as network modifiers in the metaphosphate glasses with CuO <30 mol%; the (1)Q(2) sites only exist in the glasses with high CuO content (greater than or equal to30 mol%). 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 1080 cm(-1). (C) 2003 Elsevier Science B.V. All rights reserved.