Phase equilibria in the FeNbO system at 1200°C

Abstract

Phase equilibria in the system FeNbO at 1200°C are established by changing the oxygen partial pressure from 0 to −15.00 in log ( P O 2 atm ) and are represented in the Nb 2O 5FeFe 2O 3 system. In this system, FeNbO 4, FeNb 2O 6, Fe 4Nb 2O 9, niobium-iron spinel, and NbO 2 phases appear and have non-stoichiometric compositions. Lattice constants of the compounds and the solid solutions are determined and discussed with respect to the oxygen partial pressure dependency and to the coexistence of the other compounds. The lattice constant of the spinel solid solution increases with the increasing of the content of “Fe 7Nb 2O 12.” The standard Gibbs energies of the reactions appearing in the phase diagram are calculated.