Post‐Fabrication DBD Plasma Treatment of PVDF/BaTiO 3 Nanocomposites: Composition‐Dependent Dielectric, Thermal, and Surface Responses

Poly(vinylidene fluoride) (PVDF)/BaTiO 3 composites combine polymer flexibility with ceramic polarizability, while their dielectric, thermal, and interfacial responses depend strongly on filler loading and processing history. This study investigates PVDF/BaTiO 3 composites containing 0, 5, 10, 20, and 30 vol% BaTiO 3 before and after post‐fabrication atmospheric dielectric‐barrier‐discharge (DBD) plasma treatment. The same composition series was characterized by differential scanning calorimetry, Fourier‐transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, atomic force microscopy, contact‐angle/surface‐free‐energy measurements, and dielectric spectroscopy. Mass‐fraction‐corrected PVDF crystallinity in the untreated series increased from 39.2% for neat PVDF to 45.2% at 5 vol% BaTiO 3 and then decreased to 35.9% at 30 vol%. Quantitative composition‐dependent results are based on three independently fabricated specimens per composition and treatment state ( n = 3) and are reported as mean ± standard deviation (SD). At 1 MHz, plasma treatment changed the real permittivity by 2.6%–39.4% in magnitude. Full‐frequency analysis over 20 Hz–1 MHz showed that tanδ and ε ″ decrease with increasing frequency for all compositions, whereas the loss‐derived AC conductivity, σac = 2πf ε ₀ ε ″, increases with frequency. Across the measured range, DBD treatment lowers σac for the 0, 10, 20, and 30 vol% compositions but increases it for the anomalous 5 vol% composition, demonstrating a composition‐dependent rather than uniform conductivity response. XRD and FTIR show no evidence of a new bulk crystalline phase or major bulk chemical transformation. In contrast, water contact angle decreased from 81° to 93° in untreated specimens to 44°–57° after DBD treatment, while total surface free energy increased from 29.2–37.0 mJ m −2 to 53.5–63.3 mJ m −2 , providing direct evidence of altered surface wettability. SEM and AFM further indicate composition‐dependent near‐surface morphological changes. An archived auxiliary instrument‐response channel is retained only as a relative observation because its absolute calibration could not be reconstructed and it is not interpreted as conductivity. The present results therefore support composition‐dependent dielectric, thermal, and surface modulation by DBD treatment. Surface‐/trap‐sensitive validation remains necessary before mechanism‐specific generalization, while direct breakdown testing would be required for explicit insulation‐performance claims.