2017/06/16 by Laura Uenver-Thiele, Laura Uenver‐Thiele, Alan B. Woodland +5 · 4 citations
Materials Science · Earth and Planetary Sciences · #Magnetic Properties and Synthesis of Ferrites #High-pressure geophysics and materials #Clay minerals and soil interactions
paper · doi:10.2138/am-2017-6119
Phase relations of magnesioferrite-magnetite solid solutions (Mg,Fe2+) Fe23+ O4 were investigated at pressures of 9–23 GPa and temperatures of 1200–1600 °C. Our new results indicate that the assemblage Mg2Fe2O5 + Fe2O3 reconstitutes to a hp-MgFe2O4 phase at 20 GPa and 1300–1500 °C. The stability field of hp-MgFe2O4 begins at ~1300 °C and widens to higher temperature. At lower temperature (1200–1300 °C) Mg2Fe2O5 + Fe2O3 breaks down to the new phase assemblage Mg3Fe4O9 + Fe2O3 with its stability field expanding to higher pressures and temperatures at the expense of hp-MgFe2O4. The Mg3Fe4O9 phase has the same crystal structure that recently reported for Fe7O9, and thus represents the Mg-end-member. From powder X-ray diffraction, we find that hp-MgFe2O4 has a structure consistent with an orthorhombic unit cell belonging to the Pmcn space group (no. 62). However, it could have undergone a transformation from a different structure during decompression.