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 Y₄A_l2O₉. SiC-AlN ceramics sintered with 50 wt. % SiC at 2173 K exhibited the best thermal diffusivity and thermal conductivity (26.21mm²˙s^-1 and 61.02W˙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.