Novel high pressure monoclinic Fe2O3 polymorph revealed by single-crystal synchrotron X-ray diffraction studies

作者：Bykova Elena^*; Bykov Maxim; Prakapenka Vitali; Konopkova Zuzana; Liermann Hanns Peter; Dubrovinskaia Natalia; Dubrovinsky Leonid

来源：High Pressure Research, 2013, 33(3): 534-545.

DOI：10.1080/08957959.2013.833613

• phase transition
• iron sesquioxide
• single-crystal X-ray diffraction
• laser heating
• diamond anvil cell

A novel high pressure polymorph of iron sesquioxide, m-Fe2O3, has been identified by means of single-crystal synchrotron X-ray diffraction (XRD). Upon compression of a single crystal of hematite, -Fe2O3, in a diamond anvil cell, the transition occurs at pressure of about 54GPa and results in approximate to 10% volume reduction. The crystal structure of the new phase was solved by the direct method (monoclinic space group P2(1)/n, a=4.588(3), b=4.945(2), c=6.679(7)angstrom and =91.31(9)degrees) and refined to R-1 approximate to 11%. It belongs to the cryolite double-perovskite structure type and consists of corner-linked FeO6 octahedra and FeO6 trigonal prisms filling the free space between the octahedra. Upon compression up to approximate to 71GPa at ambient temperature no further phase transitions were observed. Laser heating to approximate to 2100 +/- 100K promotes a transition to the Cmcm CaIrO3-type (post-perovskite (PPv)) phase. The PPv-Fe2O3 crystal structure was refined by means of single-crystal XRD at approximate to 65GPa. On decompression the PPv-Fe2O3 phase fully transforms back to hematite at pressures between approximate to 25 and 15GPa.

• 出版日期2013-8-20