TY - JOUR
T1 - The effect of pressure on the structure of NiAl2O4
AU - Halevy, Itzhak
AU - Dragoi, Danut
AU - Üstündag, Ersan
AU - Yue, Alan F.
AU - Arredondo, Elizabeth H.
AU - Hu, Jingzhu
AU - Somayazulu, Maddury S.
PY - 2002/11/11
Y1 - 2002/11/11
N2 - NiAl2O4 is known to transform from a normal spinel, (Ni2+)[Al23+]O4, 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.
AB - NiAl2O4 is known to transform from a normal spinel, (Ni2+)[Al23+]O4, 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.
UR - http://www.scopus.com/inward/record.url?scp=0037064895&partnerID=8YFLogxK
U2 - 10.1088/0953-8984/14/44/324
DO - 10.1088/0953-8984/14/44/324
M3 - Article
AN - SCOPUS:0037064895
SN - 0953-8984
VL - 14
SP - 10511
EP - 10516
JO - Journal of Physics Condensed Matter
JF - Journal of Physics Condensed Matter
IS - 44 SPEC ISS.
ER -