Journal
JOURNAL OF SYNCHROTRON RADIATION
Volume 16, Issue -, Pages 63-68Publisher
INT UNION CRYSTALLOGRAPHY
DOI: 10.1107/S0909049508032433
Keywords
XANES; Zn K-edge; PCA; zinc ferrite; ZnFe2O4
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Funding
- CONICET, Argentina [PIP 6524, PIP 6075]
- LNLS, Campinas, SP, Brazil [D06A-DXAS-4812, D04B-XAFS1-4148]
- ANPCyT, Argentina [PICT 38337]
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In situ Zn K-edge XANES experiments were performed to investigate the thermal evolution of the non-equilibrium state in nano-sized ZnFe2O4. The initially disordered ferrite was annealed under oxygen atmosphere and kept at temperatures of 673, 773 and 873 K. Modifications of the XANES features allowed the direct detection of the Zn local surrounding changes from O-h to T-d symmetry. Quantitative analyses of these results were performed by using the principal-component analysis approach. The ferrite inversion does not change until the activation barrier is overcome at T-a = 585 K. Above T-a, the Zn ions continuously change their environment to their normal equilibrium state. Isothermal treatments confirm that the Zn transference follows a first-order kinetic process. In addition, the thermal treatment produces a partial recrystallization that increases the average grain size from 13 to 50 nm and reduces the microstrain. The room-temperature magnetic state changes from ferrimagnetic to paramagnetic, while the blocking temperature increases after the treatment.
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