Abstract
Synchrotron radiation X-ray diffraction studies of γ-Fe2O3 have been performed with emphasis on the pressure-induced phase transformation γ(maghemite) → α(hematite) and the equation of state of the nanophase material. For γ-Fe2O3 the bulk modulus has been found to increase from 203 GPa for the bulk material to 305 GPa for 9 nm size crystals. At the same time the transition pressure decreases from 35 to 27 GPa. The reduced transition pressure is explained in terms of nucleation and growth, the larger volume change upon transition in the nanocrystalline material being the main factor.