Effects of BN Powder Morphology on the Structure and Properties of Cold‐Sintered BN‐K ₂ SO ₄ Ceramics

ABSTRACT BN‐K 2 SO 4 composite ceramics were fabricated via the cold sintering process using boron nitride (BN) powders with different morphologies. The phase composition, microstructure, thermal conductivity, and microwave dielectric properties of the ceramics were systematically investigated. The BN composite ceramics with width‐to‐thickness ratios of BN powders ranging from 33 to 1 have achieved full densification, comprising pure BN and K 2 SO 4 phases. A higher width‐to‐thickness ratio of BN powders promoted greater grain orientation within the ceramics, leading to a significant enhancement in in‐plane thermal conductivity, which reached a maximum of 32.9 W m −1 K −1 . Furthermore, BN composite ceramics prepared with the highest width‐thickness ratio exhibited superior microwave dielectric properties, with a dielectric constant of 4.6 and a Q f value of 42 182 GHz. This study clarifies the critical role of BN powder morphology in engineering the thermal conductivity and dielectric properties of BN‐based composite ceramics for advanced functional applications.