109Ag NMR investigation of tellurite glasses containing AgI or the (AgI) 0.75 (TlI) 0.25 eutectic mixture

Abstract

A 109Ag NMR investigation of [ TeO 2 R AgO 0.5] (1 − x) [ AgI] ( x) and [ TeO 2 R TlO 0.5] (1 − x) [ AgI] ( x) glasses, involving either AgI or the (AgI) 0.75(TlI) 0.25 eutectic mixture, has been carried out. The data analysis suggests a progressive crossing from an oxy-iodide environment of Ag + ions to a more and more iodide environment as AgI content increases. A quasi-linear dependence of the chemical shift of the 109Ag NMR line (δ) versus the r = (x Ag + ) AgI (x Ag + ) tot ratio indicates that a fast exchange of Ag + ions over different sites is operating at room temperature. The decrease of the 109Ag linewidth observed as x AgI increases agrees with the increase of the Ag + ion mobility deduced from conductivity data. In the [ TeO 2 R TlO 0.5] (1 − x) [( AgI) 0.75( TlI) 0.25] ( x) series containing the eutectic mixture, the value of δ (δ = 680 ppm) is independent of x AgI and close to those of α-AgI and β-AgI phases.