Thermal Conductivity and High-Frequency Dielectric Properties of Pressureless Sintered SiC-AlN Multiphase Ceramics

SiC-AlN multiphase ceramics with 10 wt. %Y₂O₃-BaO-SiO₂ additives were fabricated by pressureless sintering in a nitrogen atmosphere. The effects of SiC contents and sintering temperatures on the sinterability, microstructure, thermal conductivity and high-frequency dielectric properties were characterized. In addition to 6H-SiC and AlN, the samples also contained Y₃Al₅O₁₂ and Y₄Al₂O₉. SiC-AlN ceramics sintered with 50 wt. % SiC at 2173 K exhibited the best thermal diffusivity and thermal conductivity (26.21 mm²·s⁻¹ and 61.02 W·m⁻¹·K⁻¹, respectively). The dielectric constant and dielectric loss of the sample sintered with 50 wt. % SiC and 2123 K were 33⁻37 and 0.4⁻0.5 at 12.4⁻18 GHz. The dielectric constant and dielectric loss of the samples decreased as the frequency of electromagnetic waves increased from 12.4⁻18 GHz. The dielectric thermal conductivity properties of the SiC-AlN samples are discussed.