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Electron Holography of Potential Barriers in Zno Varistors

Published online by Cambridge University Press:  02 July 2020

M. Elfwing ,
M. Saunders  and
E. Olsson
M. Elfwing
Affiliation:
Analytical Materials Physics, Department of Materials Science, The Ångström Laboratory, Uppsala University, P. O. Box 534, SE-751 21, Uppsala, SWEDEN
M. Saunders
Affiliation:
Analytical Materials Physics, Department of Materials Science, The Ångström Laboratory, Uppsala University, P. O. Box 534, SE-751 21, Uppsala, SWEDEN
E. Olsson
Affiliation:
Analytical Materials Physics, Department of Materials Science, The Ångström Laboratory, Uppsala University, P. O. Box 534, SE-751 21, Uppsala, SWEDEN
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Extract

ZnO varistor materials are polycrystalline materials that exhibit strong non-linear current-voltage characteristics. Their non-ohmic behaviour makes them suitable for overvoltage protection devices. It is the interfaces between ZnO grains that are the key to the non-linear behaviour of the varistor materials. Previous work has shown that the local microstructure determines the breakdown voltage of the individual ZnO/ZnO interface [1]. The pre-breakdown conductivity and the non-linearity in the breakdown region, which are both crucial to the performance of the varistor, are also affected by the height and the width of the potential barriers. In the present work, electron holography has been used to investigate the potential barriers in ZnO varistor materials.

Electron holograms were recorded at 200kV using a Hitachi HF-2000 field emission gun transmission electron microscope [2]. The electrostatic bi-prism was located near the second image plane. The bi-prism voltage was about 9 V and the fringe spacing in the holograms was about 1 nm.

Type
Electron Holography
Information
Microscopy and Microanalysis , Volume 5 , Issue S2: Proceedings: Microscopy & Microanalysis '99, Microscopy Society of America 57th Annual Meeting, Microbeam Analysis Society 33rd Annual Meeting, Portland, Oregon August 1-5, 1999 , August 1999 , pp. 946 - 947
Copyright
Copyright © Microscopy Society of America

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References

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