The NQR spectra of Cu in several ErBa2Cu3O6+x powder samples (0.1≤x≤0.9), characterized by particularly careful annealing, shows a limited number of frequency peaks. This fact is taken as evidence of a high degree of ordering of O(4) in the chain Cu(1) layer of the perovskite (formation of long full chains separated by empty chains as dictated by the stoichiometry), leading to a few regular patterns in the local configurations. © 1994.
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