Magnetic Resonance and Conductivity Study of Lead-Cadmium Fluorosilicate Glasses and Glass-Ceramics

The fluorine motional dynamics in fluorosilicate glasses and glass-ceramics of the SiO2–PbF2–CdF2 system was investigated by complex impedance spectroscopy and 19F nuclear magnetic resonance (NMR) spectroscopy, and the coordination environment of a Cu2+ paramagnetic probe was examined by electron paramagnetic resonance (EPR) spectroscopy. Glass-ceramics were obtained by heat treatment of glass at a temperature between the glass-transition (Tg) and the onset of crystallization (Tx). Ionic conductivity of about 1.6 × 10–4 S/cm was obtained at 500 K for glass. The conductivity of the glass-ceramics was found to be lower than that obtained for the glass. The temperature dependence of the 19F NMR spin–lattice relaxation times was investigated between 300 and 770 K. The 19F NMR results of glass exhibit the qualitative features associated with fluorine mobility, namely, the presence of a relaxation rate maximum below Tg. The NMR relaxation data of the glass-ceramics were analyzed assuming two fluorine dynamics. Continuous-wave EPR spectroscopy, using a Cu2+ ion as a probe, was employed to determine the local symmetry of the ion environment and the nature of relevant spin interactions. The hyperfine coupling of Cu2+ with the 19F, 113Cd, and 207Pb nuclei in the glass and the glass-ceramic was investigated by electron spin echo envelope modulation and hyperfine sublevel correlation spectroscopy.