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Advances in Applied Ceramics
Structural, Functional and Bioceramics
Volume 117, 2018 - Issue 4
263
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Original Articles

Al-doped ZnO varistors prepared by a two-step doping process

ORCID Icon, ORCID Icon, , ORCID Icon, &
Pages 237-242 | Received 16 Jan 2017, Accepted 23 Oct 2017, Published online: 03 Jan 2018
 

ABSTRACT

It is difficult to dope Al into main grains of ZnO varistor ceramics, especially for small doping amount. Generally, all raw materials including Al dopant are directly mixed together and sintered into ceramics. However, in this direct doping process, Al is apt to stay in grain boundaries, and almost does not enter grains. This does harm to the electrical properties of ZnO varistors. In this paper, we proposed a two-step doping process. Al2O3 powder was first mixed only with a part of the ZnO powder and pre-sintered. The pre-sintered powder was mixed with other additives such as Bi2O3 and the rest ZnO. Then ZnO varistor ceramics were prepared via solid state sintering processes. Results showed that two-step doped ZnO varistors exhibited improved electrical properties with a significant increased nonlinear coefficient and a great decreased leakage current compared to directly doped ones because more Al was incorporated into ZnO grains.

Acknowledgement

The authors thank the Analytical and Testing Center, Huazhong University of Science and Technology for the XRD and SEM measurements.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by The National Key Research and Development Program of China [grant number 2017YFB0406301].

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