Phase equilibria in the Fe‐V‐O system near “FeO”‐V <sub>2</sub> O <sub>3</sub> isopleth
Wei Xie, Xianran Xing, Zhanmin Cao
Abstract
Abstract Phase equilibria in the “FeO”‐V 2 O 3 system from 1273 to 1808 K and in the range of oxygen partial pressure from 10 −15 to 10 −4 atm are investigated. High‐temperature quenching, XRD, SEM‐EDS, and DSC are used to determine the phase relations. Stable regions of (FeO) s.s. , (V 2 O 3 ) s.s. , and spinel phases are considerably effected by the oxygen partial pressure, and structural models are proposed as (Fe 2+ , Fe 3+ , V 2+ ) 1‐ x O, (V 2+ , V 3+ , V 4+ , Fe 3+ ) 2 O 3+ x , and (Fe 2+ , Fe 3+ , V 3+ )(Fe 2+ , Fe 3+ , V 3+ , Va) 2 O 4 . Continuous solid solution FeV 2 O 4 ‐Fe 3 O 4 is formed. The nonstoichiometry of FeV 2 O 4 is attributed to the appearance of vanadium vacancies for electroneutrality due to the oxidation of Fe 2+ . The standard Gibbs energy of formation for FeV 2 O 4 and component activities in FeV 2 O 4 ‐Fe 3 O 4 solid solution at 1623 and 1773 K are derived based on the equilibrium oxygen partial pressure. The cation distribution in FeV 2 O 4 at different temperatures is obtained according to site preference energy.