Enhanced bulk modulus and reduced transition pressure in $\gamma$-$\rm Fe_2O_3$ nanocrystals

J.Z. Jiang; J. Staun Olsen; L. Gerward; S. Mørup

doi:doi:10.1209/epl/i1998-00563-6

This article has an erratum: [erratum]

Issue		Europhys. Lett. Volume 44, Number 5, December 1998


Page(s)		620 - 626
Section		Condensed matter: structure, thermal and mechanical properties
DOI		http://dx.doi.org/10.1209/epl/i1998-00563-6

DOI: 10.1209/epl/i1998-00563-6

Europhys. Lett, 44 (5), pp. 620-626 (1998)

Enhanced bulk modulus and reduced transition pressure
in $\gamma$ - $\rm Fe_2O_3$ nanocrystals

J. Z. Jiang ¹, J. Staun Olsen ², L. Gerward ¹ and S. Mørup ¹

¹ Department of Physics, Building 307, Technical University of Denmark
DK-2800 Lyngby, Denmark
² Niels Bohr Institute, Oersted Laboratory - DK-2100 Copenhagen, Denmark

(received 5 January 1998; accepted in final form 15 October 1998)

PACS. 64.70Kb - Solid-solid transitions.
PACS. 68.35Rh - Phase transitions and critical phenomena.
PACS. 81.30 ${\rm -t}$ - Phase diagrams and microstructures developed by solidification and solid-solid phase transformations.

Abstract:

Synchrotron radiation X-ray diffraction studies of $\gamma$ - $\rm Fe_2O_3$ have been performed with emphasis on the pressure-induced phase transformation $\rm \gamma (maghemite) \to\alpha (hematite)$ and the equation of state of the nanophase material. For $\gamma$ - $\rm Fe_2O_3$ 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.

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Enhanced bulk modulus and reduced transition pressure in -nanocrystals

Abstract:

Enhanced bulk modulus and reduced transition pressure
in $\gamma$ - $\rm Fe_2O_3$ nanocrystals