Microwave Dielectric Properties of Ceramic/Semicrystalline Polymer Composites

Abstract

The effects of various ceramics and semicrystalline polymers on the dielectric properties of MgMoO 4 /polypropylene (PP), MgWO 4 /PP, NiNb 2 O 6 /poly(tetrafluoroethylene) (PTFE), and MgNb 2 O 6 /PTFE composites were investigated at microwave frequencies. In the frequency range from 1 to 9.4 GHz, the dielectric constant ( K ) of the composites showed good frequency stability, while their dielectric loss (tan δ) increased with increasing frequency, due to the dipolar relaxation process associated with the matrices. With increasing ceramic content, the K and tan δ values of the composites increased, due to the K values of the individual components and interfacial polarization between the ceramics and polymers. For the composites with the same amounts of ceramics, the K value and temperature coefficient of the resonant frequency (TCF) of the composites were dependent on the type of ceramics. Also, the measured K values of the composites were compared with the effective dielectric properties calculated by different theoretical models.