Modified poly(phenylene oxide)/(CaSr)TiO3 composites with ultrahigh permittivity and low loss for microwave substrates

Polymer/ceramic composites used as microwave dielectric combine the excellent dielectric properties of ceramic with the toughness of polymer. The properties of composites are not only determined by the properties of components but also influenced by the polymer-ceramic interface. In this work, we conducted experiments and simulations on the dielectric properties and thermal conductivity of modified poly(phenylene oxide)/(CaSr)TiO ₃ (mPPO/CST) composites. A comparison of composites filled with different sizes (2.5, 11, and 20 µm) of CST fillers demonstrates that smaller particle (more filler-matrix interface) is beneficial to mechanical properties but detrimental to dielectric properties and heat transfer. The finite element simulation results are in good agreement with the experimental values, which is of significance for guiding future experiments. The composite filled with 80 wt. % CST ₂₀ has a high relative density of 97%, an ultrahigh ε _r of ∼20, and a low tan δ of 0.0019 at 10 GHz. Meanwhile, the mPPO/CST composites are eco-friendly and suitable for mass production and are promising candidates for automotive and aerospace applications.