Phase Stability of the System Mg–Fe–O

✍ Scribed by Sun-Ho Kang; Se-Hong Chang; Han-Ill Yoo

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 220 KB
• Volume: 149
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1999.8490

✦ Synopsis

The electrical conductivity and thermoelectric power of the system Mg}Fe}O were measured as functions of oxygen activity (a O2 ) and cationic composition in the temperature range 11004T/3 3C41300. The isotherms of both electrical properties underwent a conspicuous change in trend at the same, characteristic oxygen activities, which was ascribed to a O2 -induced phase transitions from rock-salt structure to spinel structure to corrundum structure with successively increasing a O2 :s. The region of thermodynamic stability of each phase could be determined from either of the isotherms to construct phase diagrams of the 5rst kind (i.e., log a O2 vs 1/T) for 5xed compositions and the second kind (i.e., log a O2 vs composition) at 5xed temperatures. From the phase diagrams of the 5rst kind, thermodynamic quantities for a phase boundary reaction, 4Fe 3 O 4 ؉O 2 (g) ‫؍‬ 6Fe 2 O 3 , were extracted and compared with those for other systems of ferrite.