Structure and ionic conductivity of sodium titanophosphate glasses

Abstract 50Na 2 O– x TiO 2 –(50− x )P 2 O 5 (with x =0, 5, 10, 15) glasses have been characterized by infrared spectroscopy, 31 P magic angle spinning nuclear magnetic resonance (MAS–NMR) and 31 P 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 TiO 6/2 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 1,1 (Na,Ti) , even at the lowest x value. A structural unit formed by the sequence –Q 2,22 (Na) –Q 2,21 (Na) –Q 1,2 (Na,Ti) –TiO 6/2 –Q 1,1 (Na,Ti) –Q 1,1 (Na,Ti) –TiO 6/2 can be proposed. The increase of conductivity and glass transition temperature with x is discussed from this structural model.