Chain-Like Semiconductive Fillers for Dielectric Enhancement and Loss Reduction of Polymer Composites.

Dielectric composites have attracted considerable attention because of their enhanced dielectric properties, which are highly required in electrical devices and systems. Dielectric loss is a crucial factor in determining the long-term endurance for security and energy loss assessment. Here, chain-like semiconductive fibers of titanium oxide, and indium, niobium-doped titanium oxide were used for enhancing the complex dielectric properties of a polymer through composite construction, which involves significant interface enhancements. The chain-like fibers significantly enhanced the dielectric constant owing to the special morphology of the fillers and their interfacial polarization, especially at higher temperatures. The dielectric loss and electrical conductivity of the composites were substantially reduced across the entire investigated temperature range, achieved by passivating the fiber surface with an alumina shell using atomic layer deposition (ALD). The as-deposited alumina shell was transformed from an amorphous to a crystalline phase through thermal annealing. This results in a porous shell and more effective suppression of the loss tangent and electrical conductivity, indicating lowered interfacial polarization. A plausible mechanism for loss suppression is associated with carrier movement along the surface of the fibers and bulk (semiconductive fillers), leading to a larger loss tangent. The alumina shell blocked the carrier transport path, particularly at the interfaces, resulting in a reduced interfacial polarization contribution and energy storage loss. This study provides a method for inhibiting dielectric loss in dielectric composites by fabricating fillers with special shapes and surface chemistry. This article is protected by copyright. All rights reserved.