Effect of BN content on the structural, mechanical, and dielectric properties of PDCs‐SiCN(BN) composite ceramics

Abstract Hexagonal boron nitride (h‐BN) with low dielectric loss and high temperature resistance opens up new opportunities for the preparation of polymer‐derived SiCN ceramics (PDCs‐SiCN ceramics) with excellent mechanical and dielectric properties. BN‐containing polymer‐derived SiCN composite ceramics (PDCs‐SiCN(BN) composite ceramics) with different BN content were prepared via a pyrolysis process of ball‐milling‐blended Polyvinylsilazane/boron nitride (PVSZ/BN) precursors. BN is stably embedded in the SiCN tissue and tightly bound with it. The appropriate content of BN greatly improves the mechanical properties of PDCs‐SiCN ceramics, as BN reduces the number of pores and prevents crack expansion. Additionally, BN is also beneficial in lowering the dielectric loss of PDCs‐SiCN ceramics because of the weakened polarization relaxation behavior. PDCs‐SiCN (BN) composite ceramics have optimal mechanical and dielectric properties when the BN content is 1 wt%. The flexural strength, flexural modulus and compression strength of PDCs‐SiCN(BN) composite ceramics with 1 wt% BN doping content were 189.37 MPa, 46.38 GPa, and 399.02 MPa, respectively. Its average dielectric loss (tanδ ε ) at 12.4‐18 GHz is 0.0049.