CINDECA   05422
CENTRO DE INVESTIGACION Y DESARROLLO EN CIENCIAS APLICADAS "DR. JORGE J. RONCO"
Unidad Ejecutora - UE
artículos
Título:
First XANES evidence of a disorder-order transition in a spinel ferrite compound: nanocrystalline ZnFe2O4
Autor/es:
S. J. A. FIGUEROA; S. J. STEWART
Revista:
JOURNAL OF SYNCHROTRON RADIATION
Editorial:
Wiley Interscience
Referencias:
Año: 2009 vol. 16 p. 63 - 63
ISSN:
0909-0495
Resumen:
<!-- /* Font Definitions */ @font-face {font-family:"MS Mincho"; panose-1:2 2 6 9 4 2 5 8 3 4; mso-font-alt:"MS 明朝"; mso-font-charset:128; mso-generic-font-family:modern; mso-font-pitch:fixed; mso-font-signature:-536870145 1791491579 18 0 131231 0;} @font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:-1610611985 1107304683 0 0 159 0;} @font-face {font-family:"@MS Mincho"; panose-1:2 2 6 9 4 2 5 8 3 4; mso-font-charset:128; mso-generic-font-family:modern; mso-font-pitch:fixed; mso-font-signature:-536870145 1791491579 18 0 131231 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman","serif"; mso-fareast-font-family:"MS Mincho";} .MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-size:10.0pt; mso-ansi-font-size:10.0pt; mso-bidi-font-size:10.0pt;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> In situ Zn K-edge XANES experiments were performed to investigate the thermal evolution of the non-equilibrium state in nanosized ZnFe2O4. The initially disordered ferrite was annealed under oxygen atmosphere and kept at temperatures 673, 773 and 873 K. Modifications of the XANES features allowed us to directly detect the Zn local surrounding changes from Oh to Td symmetry. Quantitative analyses of these results were performed by using the PCA approach. The ferrite inversion does not change until the activation barrier is overcome at Ta = 585 K. Above Ta, the Zn ions continuously change its environment to its 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 up to 50 nm and reduces the microstrain. The room temperature magnetic state changes from ferri- to paramagnetic one, while the blocking temperature increases after the treatment.
rds']