Carbon nanotubes (CNTs) are used to prepare polymer composites with a high dielectric constant. However, a high leakage conductance is undesirable. Herein, amorphous carbon spheres were used to replace single-walled CNTs (SWCNTs) to fabricate polyvinyl chloride (PVC) composites. Two sets of composite films, marked with PVC/SWCNT and PVC/carbon sphere, were prepared. Dielectric, conductive and breakdown traits of composites were determined. PVC/carbon sphere composites display more advantageous properties than PVC/SWCNT composites. Unlike SWCNTs, carbon spheres exhibit a mild interface polarization with PVC and no percolation, resulting in balanced electric properties of composites including a rationally increased dielectric constant, greatly reduced dielectric loss and significantly improved breakdown strength. The optimal PVC composite with 12 wt% carbon spheres has a dielectric constant of ~ 186, dielectric loss of ~ 0.19 at 100 Hz, and breakdown strength of ~ 333 MV m −1 . This work boosts a large-scale fabrication of outstanding composites used in modern capacitors.
Passive electronic components made from dielectric ceramics can hardly operate at extremely high temperatures, which is attributed to the sharply increasing dielectric loss and leakage conductance. In this work, the widely applicated CaTiO 3 ceramics are used as the matrix, and the high-temperature electrical properties are modified by doping Sm 3+ and Al 3+ . The Sm-doping in CaTiO 3 ceramics can significantly suppress the dielectric relaxation at low frequencies and reduce the high-temperature leakage conductance. Continued doping of Al in Ca 0.6 Sm 0.27 TiO 3 ceramics can further reduce the high-temperature dielectric loss and conductivity. These changes are associated with tighter crystal structures and fewer defects in the ceramics. With Sm and Al doping, the high-temperature dc conductivity of the ceramics is reduced by about 4 orders of magnitude, and a dielectric loss of less than 0.02 and a low temperature cofficient of capacitance (TCC) of − 25 ppm/℃ are obtained over a wide temperature range of room temperature to 530 ℃. Outstanding temperature stabilities are exhibited over a temperature range of 25 ∼ 200 ℃ in energy storage performance and charge-discharge property. Extremely fast discharge speed ( t 0.9 = 16 ns) makes it suitable for pulsed power electronic systems. Such linear dielectric materials are expected to be used in harsh environment of high temperatures.
危险品化学品经营许可证（带存储）