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.