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 F-19 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 (T-g) and the onset of crystallization (T-x). Ionic conductivity of about 1.6 x 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 F-19 NMR spin-lattice relaxation times was investigated between 300 and 770 K. The F-19 NMR results of glass exhibit the qualitative features associated with fluorine mobility, namely, the presence of a relaxation rate maximum below T-g. 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 F-19, Cd-113, and Pb-207 nuclei in the glass and the glass-ceramic was investigated by electron spin echo envelope modulation and hyperfine sublevel correlation spectroscopy.