ELECTRIC-FIELD GRADIENTS AT CD-111 IN DELAFOSSITE OXIDES ABO(2) (A=AG, CU, B=AL, CR, FE, IN, ND, Y)

The electric-field gradient of In-111(EC)Cd-111 nuclei at cation sites in the delafossites A (B+3O2)-B-+1 have been measured using perturbed angular correlation spectroscopy. The radioactive In-111 tracers were introduced into the samples via ion implantation. The temperature dep endence of the electric-field gradient of Cd-111 in the compounds CuFe O2, CuAlO2, CuCrO2, and CuYO2 was measured in the temperature range 14 -1073 K, whereas for AgCrO2, AgInO2, and CuNdO2 only measurements at r oom temperature were carried out. In each substance at least one elect ric-field gradient with axial symmetry was found and attributed to B s ites. The scaling of this electric-field gradient with the cation-oxyg en bond length is discussed and compared with predictions of the point -charge model and measurements in binary metal oxides.