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Silicon Nitride Ceramics with High Thermal Conductivity and Excellent Mechanical Properties Fabricated with MgF2 Sintering Aid and Post-Sintering Heat Treatment
F. Hu1,2, L. Zhao1, Z.P. Xie2
1 School of Materials Science and Engineering, Jingdezhen Ceramic Institute, Jingdezhen, Jiangxi, 333001, PR China
2 State Key Lab of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, P. R. China
received August 31, 2016, received in revised form November 14, 2016, accepted November 20, 2016
Vol. 7, No. 4, Pages 423-428 DOI: 10.4416/JCST2016-00065
Abstract
Si3N4 ceramics were prepared with MgF2+Y2O3 as sintering aids by means of SPS, assisted by post-sintering heat treatment; these ceramics exhibited high thermal conductivity and excellent mechanical properties. The effect of the introduced MgF2 content and post-sintering heat treatment on the properties of Si3N4 ceramics was investigated in detail. It was found that the introduction of MgF2 had a positive impact on the growth of large elongated grains and the grain size of the Si3N4 ceramics. Compared to Si3N4 ceramics with Y2O3+MgO as sintering aids, the thermal conductivity, flexural strength and fracture toughness of the Si3N4 ceramics with Y2O3+MgF2 as sintering aids were increased by ∼ 19 %, 9 % and 12.7 %, respectively. After post-sintering heat treatments, the thermal conductivity and fracture toughness of the Si3N4 ceramics were increased by ∼ 29.9 % and 16.2 %, respectively. However, the flexural strength of the Si3N4 ceramics was reduced by ∼ 10 %. The resulting Si3N4 ceramics exhibited possessed thermal conductivity of 82.5 W·m-1·K-1, flexural strength of 911 MPa and fracture toughness of 8.47 MPa·m1/2.
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Keywords
MgF2 sintering aids, silicon nitride, thermal conductivity, mechanical properties
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