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Single-phase pyrochlore-type specimens of Bi_1.5Zn_0.92Nb_1.5O_6.92 were studied using combined electron, X-ray and neutron powder diffraction techniques. Rietveld refinements using neutron powder diffraction data confirmed an average pyrochlore structure A₂B₂O₆O′ (Fd&3macr;m, a=10.5616(1) Å) with both Bi and Zn mixed on the A-sites. However, refinements revealed significant local deviations from the ideal pyrochlore arrangement which were caused by apparent displacive disorder on both the A and O′ sites. The best fit was obtained with a disordered model in which the A-cations were randomly displaced by ∼0.39 Å from the ideal eight-fold coordinated positions. The displacements occur along the six 〈112〉 directions perpendicular to the O′–A–O′ links. In addition, the O′ ions were randomly displaced by ∼0.46 Å along all 12 〈110〉 directions. Crystal–chemical considerations suggest the …