E.S.R. investigations of γ-irradiated AgNa–Y zeolites

Abstract

Five different types of paramagnetic species related to silver nuclei were detected for γ-ray irradiated type Y zeolite in which Na⁺ ions were exchanged by Ag⁺ ions to different extents. One first species was identified as silver atoms almost freely diffusing in water contained in the zeolite cages. The second one corresponded to silver atoms interacting with lattice oxygens yet easily displaced to aluminium sites by slight warming. The unpaired spin delocalization to lattice nuclei was then rather significant at 36.3 and 21.2 %, respectiveley. The third species was assigned to Ag²⁺ ions of d⁹ character whose e.s.r. parameters reversibly depended on dehydration extent, confirming the dynamic properties of ions within zeolitic material. The fourth species was attributed to AgH⁺ arising from the action of liberated H atoms on Ag⁺. Finally, V- and F-type centres were observed, but could not be clearly identified. However, their parameters and their presence, compared to the case of non exchanged Na–Y zeolite sample, show that the electronic properties of framework nuclei are greatly perturbed by silver ions. For hydrated samples OH· radicals were also detected.