New structural and electrical data on Bi-Mo mixed oxides with a structure based on [Bi12O14](infinity) columns

We recently described a new family of oxide anion conductors with a structu re based on [Bi12O14](infinity) columns (J, Solid State Chem. 122, 394 (199 6)), The parent compound of this series can he formulated as Bi26Mo10O69 an d formation of a solid solution, in the Bi2O3-MoO3 binary system, in the ra nge 2.57 less than or equal to Bi/Mo less than or equal to 2.77 was establi shed. The stoichiometry of this series was questioned by R, Enjalbert ct al . (J, Solid State Chem. 131, 236 (1997)), but confirmed by D. J. Buttrey et al. (Mater. Res, Bull. 32, 947 (1997)). The first part of this paper is de voted to a refutation criticisms by R, Enjalbert et RI. In the second part, a comparison with other Bi2O3-based oxide anion conductors enables us to p ropose an iono-covalent description of this novel structure type, taking in to account all the structural and electrical features, especially new neutr on powder diffraction refinement and conductivity measurements under variab le oxygen partial pressures. (C) 1999 Academic Press.