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The effect of pressure on the structure of NiAl_2O_4

Halevy, Itzhak and Dragoi, Danut and Üstündag, Ersan and Yue, Alan F. and Arredondo, Elizabeth H. and Hu, Jingzhu and Somayazulu, Maddury S. (2002) The effect of pressure on the structure of NiAl_2O_4. Journal of Physics: Condensed Matter, 14 (44). pp. 10511-10516. ISSN 0953-8984. http://resolver.caltech.edu/CaltechAUTHORS:HALjpcm02

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Abstract

NiAl2O4 is known to transform from a normal spinel, (Ni2+)[Al 23+ ]O 4, to an inverse spinel, (Al3+)[Ni2+Al3+]O4, and vice versa. In this process, the larger Ni2+ ions which occupy the tetrahedral (8a) sites in normal spinel move to the octahedral (16d) sites in inverse spinel while half of the smaller Al3+ ions move in the opposite direction. The extent of this move is measured by the disorder or inversion parameter, I (the fraction of tetrahedral sites occupied by the Al ions; I = 0 for normal spinel and I = 1 for inverse spinel). Previous studies suggest that the lattice constant of spinel can decrease as the disorder parameter increases to better accommodate the Ni ions. In situ neutron diffraction studies performed by us indicate that this process is also occurring during the reduction of NiAl2O4 to Ni and Al2O3. It is possible that the compressive residual stresses generated during reduction play a role in the structural evolution of NiAl2O4. To systematically investigate the effect of pressure on the structure of NiAl2O4, x-ray diffraction studies at the X17 beamline of the National Synchrotron Light Source were performed. The pressure (up to 35 GPa) was applied via a diamond anvil cell and the experiments were conducted using a polychromatic x-ray beam. By comparing the relative intensities of certain spinel reflections that are sensitive to cationic disorder, a trend toward inverse spinel as a function of pressure was observed. The results are presented in comparison to previous studies on this material.


Item Type:Article
Alternate Title:The effect of pressure on the structure of NiAl2O4
Additional Information:© 2002 IOP Publishing Ltd. Received 24 June 2002, Published 25 October 2002, Print publication: Issue 44 (11 October 2002). The high-pressure x-ray data were collected at the National Synchrotron Light Source (NSLS) which is supported by the US Department of Energy under contract no DE-AC02-76CH00016.
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Funding AgencyGrant Number
Department of Energy (DOE)DE-AC02-76CH00016
Record Number:CaltechAUTHORS:HALjpcm02
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:HALjpcm02
Alternative URL:http://dx.doi.org/10.1088/0953-8984/14/44/324
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:527
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:12 Jul 2005
Last Modified:19 May 2017 19:18

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