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

Abstract

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