Magnetic Resonance and Conductivity Study of Lead–Cadmium Fluorosilicate Glasses and Glass-Ceramics
2018
Silva, Igor D.A. | Donoso, José Pedro | Magon, Claudio J. | Tambelli, Caio E. | Santagneli, Silvia H. | Ribeiro, Sidney J.L. | Silva, Mauricio A.P. | Chiesa, Mario | Rodrigues, Ana Candida M.
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.
Show more [+] Less [-]AGROVOC Keywords
Bibliographic information
This bibliographic record has been provided by National Agricultural Library