Effect of Hot Pressing Pressure on Microstructure and Properties of Silicon Nitride Ceramics

doi:10.16552/j.cnki.issn1001-1625.2025.0186

Abstract

Abstract: Silicon nitride (Si₃N₄) ceramics with high strength and toughness were prepared by hot pressing sintering process. The effects of hot pressing pressure on the phase composition, microstructure, mechanical properties and thermal conductivity of Si₃N₄ ceramics were studied. The results show that when the sintering temperature is 1 680 ℃ and the hot pressing pressure is between 20 MPa and 30 MPa, the α-Si₃N₄ is completely transformed into long rod-like β-Si₃N₄. With the increase of hot pressing pressure, the long-like β-Si₃N₄ grains developed completely, the porosity decreases, and the density increases. At the same time, in the process of hot pressing sintering, the grain growth of β-Si₃N₄ is oriented, and the crystal prism surface is perpendicular to the direction of hot pressing. When the hot pressing pressure is 30 MPa, the comprehensive performance of Si₃N₄ ceramics is the best, the bending strength is 1 123.72 MPa and the fracture toughness is 11.6 MPa·m^1/2, the Vickers hardness perpendicular to the hot pressing direction is 14.42 GPa, and the thermal conductivity at room temperature is 44.2 W/(m·K). By changing the content of single-phase sintering additives, the thermal conductivity of Si₃N₄ ceramics prepared by selecting Y₂O₃-MgO sintering additives under the same conditions is greatly improved, up to 62.9 W/(m·K).

Key words: Si₃N₄ ceramics, hot pressing sintering, hot pressing pressure, microstructure, mechanical property, thermal conductivity

CLC Number:

TQ174

ZANG Xiangrong, YU Zhiqiang, LI Haiqing, TAN Huihui, LU Yanping, PENG Zihan. Effect of Hot Pressing Pressure on Microstructure and Properties of Silicon Nitride Ceramics[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2025, 44(9): 3383-3390.

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