ESR of copper-doped β-alumina localization of Cu2+ and linewidth effect

β-alumina single crystals doped with Cu2+ ions and annealed are studied by EPR. In these crystals, Cu2+ ions occupy one site called A which is different from the B- and B'-sites found immediately after chemical exchange, sites which were studied previously. g and hyperfine tensors are of rhombic symmetry and the ground state of Cu2+ is predominantly dx2 – y2. This A-site is attributed to a mO position distorted by a relaxation of the first-neighbour oxygen ions which are along the a-direction in the conduction plane. This distortion leads to a distribution of the linewidth within the hyperfine multiplet which is analyzed in terms of a distribution of the g and hyperfine parameters.