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The pressure induced transformation of the rare β Fe2O3 phase

The pressure-induced transformation of the rare β-Fe2O3 phase has been studied for the first time, leading to the identification of a new iron(III) oxide polymorph, ζ-Fe2O3. The transformation of β-Fe2O3 into ζ-Fe2O3 occurs above 30 GPa, and the new phase withstands pressures of up to ~70 GPa, which is well above the thresholds for the pressure-induced transformations of α-Fe2O3 or γ-Fe2O3. More strikingly, ζ-Fe2O3 remains stable after pressure release and at room temperature. This remarkable observation is explained in terms of its Gibbs free energy (and surface energy), partly due to structural properties inherited from its precursor material (small β-Fe2O3 nanoparticles) and partly due to stabilizing structural changes during high-pressure treatment. Its stability is thus strongly linked to the nanoscale dimensions of its particles. It has a monoclinic crystal structure belonging to the I2/a space group (a = 9.683 Å, b = 10.00 Å, c = 8.949 Å, β = 101.10° and V = 850.4 Å3). The ζ-Fe2O3 phase behaves in an antiferromagnetic manner with a Néel transition temperature of ~69 K. It may also have other interesting electronic, optical, and transport properties that would lend themselves to practical applications. Thus, in the future, two challenges are viewed to be of significant importance in stimulating further research in the iron(III) oxide realm: (i) to develop new methods for preparing ζ-Fe2O3 from ultrafine β-Fe2O3 nanoparticles, possibly by exploiting spatial restrictions, controlling the level of interparticle interactions (aggregation) during transformation and using thermal rather than pressure treatment; and (ii) to study the pressure-induced transformations of rare ε-Fe2O3. If you are looking for high quality, high purity, and cost-effective Iron oxide, or if you require the latest price, please feel free to email contact mis-asia.

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