Phase relations in the “FeO–V2O3” system at 1473 K and the magnetic properties of spinel phase Fe3-V O4

Experimental Determination of the Standard Gibbs Energy of Formation of Fe3–xVxO4 at 1473 K

“…Regarding the parameters y s and µ V, y s , they can be determined by using the following approaches. For y s , it can be read directly from the phase diagram of the Fe t O-V 2 O 3 system at 1473 K under various oxygen partial pressures, which we have reported in a previous publication [21]. For µ V, y s , it can be determined by the formation reaction of V 2 O 3 shown as Equation ( 9), because the chemical potentials of V in all the equilibrated phases are equal.…”

“…Pure Fe 3-x V x O 4 compounds with different Fe/V molar ratios were prepared through the conventional solid-state reaction method under CO-CO 2 gas mixture atmosphere at 1473 K, where CO-CO 2 gas mixture was adopted to control the oxygen partial pressure in the reaction chamber. The experimental apparatus and the operating details can be found in our previous publications [21,28,29]. The reactants, composed of analytical reagents of Fe, Fe 2 O 3 , and V 2 O 3 with purity of 99.99%, were ground homogeneously in an agate mortar and pressed into pellets.…”

“…In our previous publication [21], the phase diagram of the "FeO"-V 2 O 3 system at 1473 K in the oxygen partial pressure range of 5.98 × 10 −15 atm to 2.39 × 10 −8 atm was reported. Under the present investigated oxygen partial pressures, the Fe/V molar ratio for the single-phase area of Fe 3-x V x O 4 is summarized in Table 2.…”

“…Furthermore, according to the relationship between µ O 2 and oxygen partial pressure, Equation ( 20) can be changed to Equation (21).…”

“…Wakihara et al [20] determined the phase equilibria in FeO-Fe 2 O 3 -V 2 O 3 system at 1500 K by varying the oxygen partial pressure and proposed the phase boundaries of Fe 3-x V x O 4 . In our previous publication [21], the phase equilibria of the FeO-V 2 O 3 system at 1473 K under various oxygen partial pressures were determined, and a phase diagram of lg p O 2 /atm vs. the molar ratio of V/(Fe + V) was presented. Based on the available phase equilibria and thermodynamic data, the Fe-V-O system was assessed and optimized through the CALPHAD method.…”