Effects of MgO addition on the microwave dielectric properties of high thermal-conductive silicon nitride ceramics sintered with ytterbia as sintering additives

1mol% of MgO was added together with 7mol% of Yb2O3 as sintering additives to silicon nitride powder to fabricate advanced silicon nitride ceramics with both high thermal conductivity and low dielectric loss at 2GHz. The mixed powder was CIPed at a pressure of 120MPa and was gas-pressure sintered at...

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Bibliographic Details
Published in:Journal of the European Ceramic Society 2012-09, Vol.32 (12), p.3297-3301
Main Authors: Miyazaki, Hiroyuki, Hirao, Kiyoshi, Yoshizawa, Yu-ichi
Format: Article
Language:English
Subjects:
Dielectric properties
Insulators
Si3N4
Sintering
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Summary:1mol% of MgO was added together with 7mol% of Yb2O3 as sintering additives to silicon nitride powder to fabricate advanced silicon nitride ceramics with both high thermal conductivity and low dielectric loss at 2GHz. The mixed powder was CIPed at a pressure of 120MPa and was gas-pressure sintered at 1900°C to >98% of theoretical density. The sintered Si3N4 sample exhibited a high thermal conductivity of ∼100Wm−1K−1 and a loss tangent (tanδ) of ∼4×10−4, concurrently. The tanδ was further reduced by half after the heat treatment at 1300°C for 24h. The improvement in tanδ due to the annealing was explained from the point of crystallization of the intergranular glassy phase.
ISSN:0955-2219
1873-619X
DOI:10.1016/j.jeurceramsoc.2012.04.025