Dielectric and Mechanical Properties of Porous Si₃N₄-BN Ceramic Composites

Abstract:

Recently, ceramic composites with low dielectric constant, low loss tangent, high flexural strength and high thermal shock resistance have received a considerable attention as candidate materials for certain high speed radome. In this paper, Si₃N₄-BN ceramic composites were fabricated by dry-press processing and cold isostatic pressing, with α-Si₃N₄ and BN as starting powder, Al₂O₃ and Yb₂O₃ as sintering additives, PMMA as pore-forming agen_{Subscript text}t. After sintering for 2 h at 1750°C, porous Si₃N₄-BN ceramic composites with a three-point bending strength of 50~120MPa and a dielectric constant of 3.2~4.4 at 7~18 GHz frequency were obtained. The sintered body was mainly β-Si₃N₄ grains; BN was dispersed in the grains. The formation of β-Si₃N₄ grains was demonstrated by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) respectively. Furthermore, the influence of the BN content on the dielectric and mechanical properties was also studied. The porous Si₃N₄-BN ceramic composites showed a lower dielectric constant and shrinkage. For above excellent properties, Si₃N₄-BN ceramic composites have been became one of the most hopeful candidate materials for high speed radome.

• Periodical: Key Engineering Materials (Volumes 512-515)
• Pages: 854-857
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.512-515.854
• Online since: June 2012
• Authors: Jian Peng Dou, Xiao Lin Liu, Jing Tao Ma, Xu Ping Lin
• Keywords: Si₃N₄, BN, Ceramic Composites, Radome

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