Microstructure and Dielectric Properties of LPCVD/CVI-SiBCN Ceramics Annealed at Different Temperatures

• Main Authors: Jianping Li, Mingxi Zhao, Yongsheng Liu, Nan Chai, Fang Ye, Hailong Qin, Laifei Cheng, Litong Zhang
• Format: Article
• Language: English
• Published: MDPI AG 2017-06-01
• Series: Materials
• Subjects: siliconboron carbonitride ceramic; dielectric properties; electromagnetic wave absorbing properties; heat treatment; chemical vapor deposition and infiltration
• Online Access: http://www.mdpi.com/1996-1944/10/6/655
• ISSN: 1996-1944

SiBCN ceramics were introduced into porous Si3N4 ceramics via a low-pressure chemical vapor deposition and infiltration (LPCVD/CVI) technique, and then the composite ceramics were heat-treated from 1400 °C to 1700 °C in a N2 atmosphere. The effects of annealing temperatures on microstructure, phase evolution, dielectric properties of SiBCN ceramics were investigated. The results revealed that α-Si3N4 and free carbon were separated below 1700 °C, and then SiC grains formed in the SiBCN ceramic matrix after annealing at 1700 °C through a phase-reaction between free carbon and α-Si3N4. The average dielectric loss of composites increased from 0 to 0.03 due to the formation of dispersive SiC grains and the increase of grain boundaries.