Trivalent cation substitution of pulverulent cobalt-iron molybdates Co1-xFexMoO4

摘要

Different mixed cobalt-iron molybdates Co1-xFexMoO4 (O less than or equal to x less than or equal to 1) have been prepared by means of a ceramic process. The oxidation of pulverulent samples leads to ferric molybdate Fe-2(oO(4))(3), spinelle Co3O4 and cobalt molybdate CoMoO4. After a strong grinding which reduces the grain size (about 0.1 mu m) and induces crystallographic defects in the grains, the cobalt-iron molybdates can be partially oxidized into cation-deficient phases. This oxidation corresponds to an isostructural substitution of part of the Fe2+ and Co2+ ions by Fe3+ and Co3+ ions and the creation of cation vacancies. The concomitant presence of trivalent cations and associated cation Vacancies in the lattice stabilizes the highest-temperature variety of the cobalt or iron molybdates, i.e., the a variety. (C) 1998 Elsevier Science S.A. All rights reserved. References: 35