EPR of Ag²⁺ in β-alumina

EPR measurements have been made on Ag²⁺ in sodium beta -alumina single crystals. Silver is introduced into the conduction plane as Ag ⁺ by exchange with Na⁺ in amounts varying from 5 to 26%: Ag²⁺ is produced by X-ray irradiation at 300K. EPR results indicate that the Ag²⁺ occupies two sites of orthorhombic symmetry in the conduction plane. The measured g-values are g_x=2.0230(2), g _y=2.0678(15), g_z=2.2730(5) and g_x=2.015(4), g_y=2.0580(15), g_z=2.2335(4) where x, y, z are parallel to a*, c, a axes respectively. The hyperfine interaction with the ¹⁰⁷Ag nuclei is unresolved and estimated to be less than 1 mT. No motional effects are observed. Models are discussed for the two sites which involve an excess of O^2- ions in the conduction plane.