On the role of grain boundaries in nanocrystalline γ-Fe 2O 3 under high pressure

Dongmei Zhang; Yongsheng Zhang; Yang Gao; Yonghao Han; Chunxiao Gao; Yanzhang Ma; Chunxiao Cheng; Ke Yu

doi:10.1063/1.3695459

On the role of grain boundaries in nanocrystalline γ-Fe ₂O ₃ under high pressure

Dongmei Zhang, Yongsheng Zhang, Yang Gao, Yonghao Han, Chunxiao Gao, Yanzhang Ma, Chunxiao Cheng, Ke Yu

Mechanical Engineering

Research output: Contribution to journal › Article › peer-review

6 Scopus citations

Abstract

In situ impedance spectroscopy of nanophase and bulk γ-Fe ₂O ₃ were performed using a fabricated microcircuit on a diamond anvil cell. The results provide evidence for the existence of grain and grain boundary effects that are separated in the frequency region. The analysis establishes that the grain boundary conductance of nanocrystalline γ-Fe ₂O ₃ is higher than that of the bulk material. Both the grain and grain boundary resistances of γ-Fe ₂O ₃ smoothly decrease with pressure. A remarkable phenomenon of discontinuity appears at 7.4 GPa for the nanocrystals. This critical value is interpreted by the space charge model and changes in charge densities between the grain boundaries. The impedance analysis further reveals that the relaxation frequency gradually increased with the effect of pressure and the γ-Fe ₂O ₃ samples' impedance imaginary part exhibits a typical capacitive characteristic. Within the given pressure range, the relaxation frequency of γ-Fe ₂O ₃ follows the Arrhenius behavior. This result was attributed to a dominant interfacial effect.

Original language	English
Article number	063718
Journal	Journal of Applied Physics
Volume	111
Issue number	6
DOIs	https://doi.org/10.1063/1.3695459
State	Published - Mar 15 2012

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title = "On the role of grain boundaries in nanocrystalline γ-Fe 2O 3 under high pressure",

abstract = "In situ impedance spectroscopy of nanophase and bulk γ-Fe 2O 3 were performed using a fabricated microcircuit on a diamond anvil cell. The results provide evidence for the existence of grain and grain boundary effects that are separated in the frequency region. The analysis establishes that the grain boundary conductance of nanocrystalline γ-Fe 2O 3 is higher than that of the bulk material. Both the grain and grain boundary resistances of γ-Fe 2O 3 smoothly decrease with pressure. A remarkable phenomenon of discontinuity appears at 7.4 GPa for the nanocrystals. This critical value is interpreted by the space charge model and changes in charge densities between the grain boundaries. The impedance analysis further reveals that the relaxation frequency gradually increased with the effect of pressure and the γ-Fe 2O 3 samples' impedance imaginary part exhibits a typical capacitive characteristic. Within the given pressure range, the relaxation frequency of γ-Fe 2O 3 follows the Arrhenius behavior. This result was attributed to a dominant interfacial effect.",

author = "Dongmei Zhang and Yongsheng Zhang and Yang Gao and Yonghao Han and Chunxiao Gao and Yanzhang Ma and Chunxiao Cheng and Ke Yu",

note = "Funding Information: The authors acknowledge the financial support from the NSF of China (Grant Nos. 10874053, 11074094, 50802033, 91014004, and 60876014)), the National Basic Research Program of China (Grant No. 2005CB724404), and the NSF of Henan province (Grant Nos. 072300410180, 2010B140009). The project is also sponsored by Program for Science & Technology Innovation Talents in Universities of Henan Province (Grant No. 2008HASTIT029), and the Innovation Scientists and Technicians Troop Construction Projects of Henan Province (No. 104100510018).",

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AU - Zhang, Dongmei

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AU - Gao, Yang

AU - Han, Yonghao

AU - Gao, Chunxiao

AU - Ma, Yanzhang

AU - Cheng, Chunxiao

AU - Yu, Ke

N1 - Funding Information: The authors acknowledge the financial support from the NSF of China (Grant Nos. 10874053, 11074094, 50802033, 91014004, and 60876014)), the National Basic Research Program of China (Grant No. 2005CB724404), and the NSF of Henan province (Grant Nos. 072300410180, 2010B140009). The project is also sponsored by Program for Science & Technology Innovation Talents in Universities of Henan Province (Grant No. 2008HASTIT029), and the Innovation Scientists and Technicians Troop Construction Projects of Henan Province (No. 104100510018).

PY - 2012/3/15

Y1 - 2012/3/15

N2 - In situ impedance spectroscopy of nanophase and bulk γ-Fe 2O 3 were performed using a fabricated microcircuit on a diamond anvil cell. The results provide evidence for the existence of grain and grain boundary effects that are separated in the frequency region. The analysis establishes that the grain boundary conductance of nanocrystalline γ-Fe 2O 3 is higher than that of the bulk material. Both the grain and grain boundary resistances of γ-Fe 2O 3 smoothly decrease with pressure. A remarkable phenomenon of discontinuity appears at 7.4 GPa for the nanocrystals. This critical value is interpreted by the space charge model and changes in charge densities between the grain boundaries. The impedance analysis further reveals that the relaxation frequency gradually increased with the effect of pressure and the γ-Fe 2O 3 samples' impedance imaginary part exhibits a typical capacitive characteristic. Within the given pressure range, the relaxation frequency of γ-Fe 2O 3 follows the Arrhenius behavior. This result was attributed to a dominant interfacial effect.

AB - In situ impedance spectroscopy of nanophase and bulk γ-Fe 2O 3 were performed using a fabricated microcircuit on a diamond anvil cell. The results provide evidence for the existence of grain and grain boundary effects that are separated in the frequency region. The analysis establishes that the grain boundary conductance of nanocrystalline γ-Fe 2O 3 is higher than that of the bulk material. Both the grain and grain boundary resistances of γ-Fe 2O 3 smoothly decrease with pressure. A remarkable phenomenon of discontinuity appears at 7.4 GPa for the nanocrystals. This critical value is interpreted by the space charge model and changes in charge densities between the grain boundaries. The impedance analysis further reveals that the relaxation frequency gradually increased with the effect of pressure and the γ-Fe 2O 3 samples' impedance imaginary part exhibits a typical capacitive characteristic. Within the given pressure range, the relaxation frequency of γ-Fe 2O 3 follows the Arrhenius behavior. This result was attributed to a dominant interfacial effect.

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On the role of grain boundaries in nanocrystalline γ-Fe ₂O ₃ under high pressure

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