The O-deficient pyrochlore, Bi2Ru2O7-y, was prepared by heating mixtures of Bi2O3 and RuO2 at 1000C in air, followed by treatment under Ar. The structure was cubic (a = 1.02991nm, Fd¯3m). Profile refinement of neutron diffraction data indicated a significant O-vacancy content of y = 0.20; with the vacancies distributed at random over the 8a positions. Accurate Ru-O and Bi-O interatomic distances, and a bond-valence study, indicated an oxidation state, for Ru cations, that was lower than 4+. This was consistent with the presence of O vacancies in the structure, and with an increase in the lattice parameter with respect to the stoichiometric material.

Oxygen Vacancy Control in the Defect Bi2Ru2O7-y Pyrochlore: a Way to Tune the Electronic Bandwidth. R.E.Carbonio, J.A.Alonso, J.L.Martínez: Journal of Physics - Condensed Matter, 1999, 11[2], 361-9