Cost‐Effective Polymer‐Derived SiBON Ceramics With Low Carbon and Low Dielectric Loss

ABSTRACT SiBON ceramics exhibit excellent high‐temperature resistance, thermal shock resistance, and wave‐transparent properties, making them promising materials for radome materials under hypersonic flight conditions. In this study, a novel boronic acid‐modified polysilazoxane (RBOSZ) was synthesized via the polymer‐derived ceramics (PDC) route using cost‐effective starting materials, including trichlorosilane, tert‐butanol, boric acid, and ammonia. The polymer features a Si–N–Si backbone with tert‐butoxy side groups. After pyrolysis under nitrogen atmosphere, RBOSZ was converted into SiBON ceramics with a low residual carbon content of 0.65 wt% and a ceramic yield of 70.5 wt%. The introduction of boric acid increased the oxygen content of the precursor, promoting the formation of the Si 2 N 2 O phase at high temperatures. The RBOSZ‐derived ceramics exhibited remarkable thermal stability, retaining an amorphous structure up to 1400°C and forming Si 2 N 2 O nanocrystals after annealing at 1600°C. After treatment at 1700°C, the mass retention reached 81.2 wt%, significantly higher than that of the unmodified polysilazoxane (47.2 wt%). Furthermore, the ceramics demonstrated favorable wave‐transparent properties, with a dielectric constant (ε) of 3.5–4.0 and a loss tangent (tan δ) of 0.0029–0.0071 in the frequency range of 8–12 GHz.