Structure and ionic conductivity of sodium titanophosphate glasses

50Na2O–xTiO2–(50−x)P2O5 (with x=0, 5, 10, 15) glasses have been characterized by infrared spectroscopy, 31P magic angle spinning nuclear magnetic resonance (MAS–NMR) and 31P double-quantum (DQ) MAS–NMR. MAS–NMR 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 Qn,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 Q1,1(Na,Ti), even at the lowest x value. A structural unit formed by the sequence –Q2,22(Na)–Q2,21(Na)–Q1,2(Na,Ti)–TiO6/2–Q1,1(Na,Ti)–Q1,1(Na,Ti)–TiO6/2 can be proposed. The increase of conductivity and glass transition temperature with x is discussed from this structural model.