Structure and ionic conductivity of sodium titanophosphate glasses

50Na(2)O-xTiO(2)-(50 - x)P2O5 (with x = 0, 5, 10, 15) glasses have been characterized by infrared spectroscopy, P-31 magic angle spinning nuclear magnetic resonance (MAS-NMR) and P-31 double-quantum (DQ) MAS-NMR. MASNMR spectra show that phosphate network depolymerization occurs when x increases. Infrared spectra indicate that titanium is incorporated as TiO6/2 units. DQ MAS-NMR enables us to characterize the Q(n.ij) phosphate units. Their chemical shifts, measured on DQ MAS-NMR spectra, were used as constraints for the deconvolution of one-dimensional MAS-NMR spectra. It indicates the formation of diphosphate units bonded to sodium and titanium Q({Na,Ti})(1.1) even at the lowest x value. A structural unit formed by the sequence -Q({Na})(2.22) -Q({Na})(2.21) -Q({Na.Ti})(1.2) -TiO6,2 -Q({Na,Ti})(1.1) -Q({Na, Ti})(1.1) -TiO6,2 can be proposed. The increase of conductivity and glass transition temperature with x is discussed from this structural model. (C) 2001 Elsevier Science B.V. All rights reserved.