Obtaining Greatly Improved Dielectric Constant in BaTiO₃–Epoxy Composites with Low Ceramic Volume Fraction by Enhancing the Connectivity of Ceramic Phase

Ceramic–polymer dielectric composites show promising potential as embedded capacitors, whereas it is a great challenge to obtain a high dielectric constant (εr) at a low ceramic volume fraction (Vc). This work demonstrates a strategy for overcoming this challange. By employing a high sintering temperature (Ts) and introducing porogen, BaTiO3 ceramics with both great connectivity and high porosity are obtained, and the composites with improved εr at a low Vc are prepared after curing the epoxy monomer, which is infiltrated into the porous ceramic bodies. For the composite with a Ts of 1300 °C and a Vc of 38.1%, the εr is as high as 466.8 at 1 kHz, which is improved by about nine times compared to the 0–3 counterpart with a higher Vc of 60.8%. Furthermore, the composite exhibits low dielectric loss and good frequency and temperature stability of εr, indicating the great potential for practical applications. Finite element simulation shows that the enhanced connectivity of BaTiO3 increases the electric field intensity in high-εr BaTiO3 dramatically and therefore plays a key role in the dielectric response of the composite. This work not only sheds light on the high-εr ceramic–polymer composites but also deepens the understanding on the relationship between their properties and microstructures.