ENDOR measurements of defects in sodium β-alumina. I

ENDOR, ENDOR-induced EPR and EPR measurements show that X-irradiation at room temperature of sodium beta -alumina single crystals produces four different paramagnetic defects. One of these is a defect at the O(5) site, probably an F + centre. Its interaction with the nearest Na and Al nuclei is determined from the ENDOR spectrum. Using the special technique of ENDOR-induced EPR the electric field gradient at these Na nuclei is found to be (0.7+or-0.1)*10 40 Vm -2 C -1 . A second defect is tentatively identified as an O 2 - ion in the conduction plane. Models are proposed for the two other defects.