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Microstructure, Thermal Conductivity, and Electrical Properties of In Situ Pressureless Densified SiC–BN Composites
Author(s) -
Li Yinsheng,
Yin Jie,
Wu Haibo,
Zhang Jingxian,
Chen Jian,
Yan Yongjie,
Liu Xuejian,
Huang Zhengren,
Jiang Dongliang
Publication year - 2015
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.13376
Subject(s) - materials science , microstructure , composite material , dielectric , electrical resistivity and conductivity , dielectric loss , thermal conductivity , electrical engineering , optoelectronics , engineering
The microstructure, thermal conductivity, and electrical properties of pressureless densified SiC– BN composites prepared from in situ reaction of Si 3 N 4 , B 4 C, and C were systematically investigated, to achieve outstanding performance as substrate materials in electronic devices. The increasing BN content (0.25–8 wt%) in the composites resulted in finer microstructure, higher electrical resistivity, and lower dielectric constant and loss, at the expense of only slight degradation of thermal conductivity. The subsequently annealed composites showed more homogeneous microstructures with less crystal defects, further enhanced thermal conductivities and electrical resistivities, and reduced dielectric constants and losses, compared with the unannealed ones. The enhanced insulating performance, the weakened interface polarization, and the reduced current conduction loss were explained by the gradual equalization of dissolved B and N contents in SiC crystals and the consequent impurity compensation effect. The schottky contact between graphite and p ‐type SiC grains presumably played a critical role in the formation of grain‐boundary barriers. The annealed composites doped with 8 wt% BN exhibited considerably high electrical resistivity (4.11 × 10 11 Ω·cm) at 100 V/cm, low dielectric constant (16.50), and dielectric loss (0.127) at 1 MHz, good thermal conductivity [66.06 W·(m·K) −1 ] and relatively high strength (343 MPa) at room temperature.