Construction of a flexible 1D core–shell Al2O3@NaNbO3 nanowire/poly(p-phenylene benzobisoxazole) nanocomposite with stable and enhanced dielectric properties in an ultra-wide temperature range

Abstract

Polymeric dielectrics with high-temperature resilience are of critical importance in developing advanced electrostatic capacitors. Poly(p-phenylene benzobisoxazole) (PBO) is a polymer with excellent thermal stability. However, poor processability and low intrinsic dielectric constant restrict its application in high-performance dielectrics. In this study, PBO is synthesized by the precursor method, and the polymer films are prepared via solution casting which is more convenient than the traditional processing method. Moreover, a hierarchically structured one-dimensional Al₂O₃@NaNbO₃ is designed and introduced into the PBO matrix. Due to the high aspect ratio and the unique structure of Al₂O₃@NaNbO₃, the dielectric properties and breakdown strength of the nanocomposite have been substantially increased. The nanocomposite filled with 3 vol% Al₂O₃@NaNbO₃ possesses the highest breakdown strength of 286 kV mm⁻¹ while maintaining a high dielectric constant of 6.68 and a low dielectric loss of 0.035 at 1 kHz, and the energy density increased to 1.64 J cm⁻³ at 250 kV mm⁻¹ (≈200% higher than that of pure PBO). In addition, the dielectric properties of 3 vol% Al₂O₃@NaNbO₃–PBO exhibit excellent thermal stability from 25 to 250 °C which is attributed to the thermal resistance of both PBO and Al₂O₃@NaNbO₃. This work provides a promising way to fabricate polymeric dielectrics for use in extreme environments.