Electrical property of nanocrystalline γ-Fe2O3 under high pressure

Using a microcircuit fabricated on a diamond anvil cell, in situ conductivity measurements on nanophase (NP) gamma-Fe2O3 are obtained under high pressure. For NP gamma-Fe2O3, the abrupt increase in electrical conductivity occurs at a pressure of 21.3 GPa, corresponding to a transition from maghemite to hematite. Above 26.4 GPa, conductivity increases smoothly within creasing pressure. No distinct abnormal change is observed during decompression, indicating that transformation is irreversible. The temperature-dependence of the conductivity of NP gamma-Fe2O3 was investigated at several pressures, indicating the electrical conductivity of the sample increases with increasing pressure and temperature, and that are markable phenomenon of discontinuity occurs at 400 K. The abnormal change is attributed to the electronic phase transitions of NP gamma-Fe2O3 due to the variation of inherent cation vacancies. Besides, the temperature-dependence of the electrical conductivity displays semiconductor-like behavior before 33.0 GPa. (c) 2012 Elsevier B.V. All rights reserved.