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Annealing and firing in wet hydrogen are widely used steps in the processing alumina–ceramic insulators that may affect their dielectric breakdown strengths (DBS). In this study, the effects of annealing (at 1300 ℃ for 7 h) and firing in wet hydrogen on the DBS of alumina ceramics (all sintered at 1650 ℃) were studied, and the underlying mechanisms were analyzed by material characterizations. Annealing reduced the DBS of the 95% alumina ceramics due to the inter-granular phase crystallization, and the reduction in the DBS could be correlated to the reduction in mechanical strength. In contrast, annealing improved the DBS of the 99% alumina ceramic without intergranular phase transformation. Firing in wet hydrogen at 1500 ℃ caused the DBS increment, which can be ascribed to the reduction in the concentrations of point defects and electrical carriers.


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Effects of annealing and firing in wet hydrogen on the dielectric breakdown strengths of alumina ceramics

Show Author's information Jishi DUa( )Binghua TANGaWei LIUaTao ZHANGa,bJiagen PENGaHu CHENaYangjun LEIa
Institute of Electronic Engineering, China Academy of Engineering Physics, Mianyang 621900, China
Department of Materials Science, Sichuan University, Chengdu 610064, China

Abstract

Annealing and firing in wet hydrogen are widely used steps in the processing alumina–ceramic insulators that may affect their dielectric breakdown strengths (DBS). In this study, the effects of annealing (at 1300 ℃ for 7 h) and firing in wet hydrogen on the DBS of alumina ceramics (all sintered at 1650 ℃) were studied, and the underlying mechanisms were analyzed by material characterizations. Annealing reduced the DBS of the 95% alumina ceramics due to the inter-granular phase crystallization, and the reduction in the DBS could be correlated to the reduction in mechanical strength. In contrast, annealing improved the DBS of the 99% alumina ceramic without intergranular phase transformation. Firing in wet hydrogen at 1500 ℃ caused the DBS increment, which can be ascribed to the reduction in the concentrations of point defects and electrical carriers.

Keywords:

alumina ceramic, dielectric breakdown strength (DBS), inter-granular phase crystallization, firing in wet hydrogen
Received: 15 November 2019 Revised: 24 December 2019 Accepted: 26 December 2019 Published: 07 April 2020 Issue date: April 2020
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Publication history

Received: 15 November 2019
Revised: 24 December 2019
Accepted: 26 December 2019
Published: 07 April 2020
Issue date: April 2020

Copyright

© The author(s) 2019

Acknowledgements

The study was financially supported by the Science Development Foundation of China Academy of Engineering Physics (2014A0302012) and the Funding Support by Laboratory of Precision Manufacturing Technology, CAEP (ZD18001). The authors also gratefully acknowledge the assistance from Mr. Kang Peng in the DB test. We thank Dr. Yuefang Li for her help in writing the paper.

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