Variation of porosity and pore size during post-sintering of reaction-bonded silicon nitride doped with Y2O3 and MgO additives

Sintering of reaction-bonded silicon nitride (SRBSN) is a method of preparing Si3N4 ceramics with high thermal conductivity and good mechanical properties. In the present study, by using a high purity silicon powder as the starting material and 2 mol % of Y2O3 and 5 mol % of MgO as sintering additiv...

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Bibliographic Details
Published in:Journal of the Ceramic Society of Japan 2020/02/01, Vol.128(2), pp.75-79
Main Authors: MATSUNAGA, Chika, ZHOU, You, KUSANO, Dai, HYUGA, Hideki, HIRAO, Kiyoshi
Format: Article
Language:English
Subjects:
Additives
Ceramic bonding
Coalescing
Densification
Grain growth
Magnesium oxide
Mechanical properties
Nitridation
Phase transitions
Pore size
Porosity
Reaction bonding
Silicon
Silicon nitride
Sintering
Sintering (powder metallurgy)
Thermal conductivity
Yttrium oxide
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Summary:Sintering of reaction-bonded silicon nitride (SRBSN) is a method of preparing Si3N4 ceramics with high thermal conductivity and good mechanical properties. In the present study, by using a high purity silicon powder as the starting material and 2 mol % of Y2O3 and 5 mol % of MgO as sintering additives, the phenomena including phase transformation, grain growth, densification, and pore size evolution occurred in the SRBSN process were studied. It was found that the α- to β-Si3N4 phase transformation could complete at 1700°C. Obvious grain growth started at around 1700°C. Substantial densification took place at temperatures between 1800 and 1900°C. When sintered at 1900°C for 30 min, not only the total number of pores drastically decreased as a result of the shrinkage of the compact, but also a fraction of open pores turned to be closed pores due to microstructural changes such as grain growth and pore coalescence.
ISSN:1882-0743
1348-6535
DOI:10.2109/jcersj2.19036