Broadband dielectric response of silk Fibroin/BaTiO3 composites: Influence of nanoparticle size and concentration

In order to advance towards more sustainable electronics generation, natural polymers with tailored dielectric response are essential. In this search, the combination of bio-based materials with active fillers in composite form, suppose one of the most viable alternatives. To achieve it, this work has explored the ability to control dielectric response of Silk Fibroin, a protein polymer by its combination with ceramic barium titanate (BaTiO3) nanoparticles. Both the effect of filler concentration (0, 5, 10, 20 and 40 wt%) and size (100 and 200 nm) has been studied in composites processed by easily scalable techniques. Samples with a homogeneous distribution of nanoparticles have been obtained. Dielectric relaxation processes assessed by broadband dielectric relaxation spectroscopy (BDS) in wide frequency (0.1 Hz–1 MHz) and temperature ranges (- 40 to 220 °C), revealed a dielectric constant increasing with filler content and decreasing with filler size, ranging from 4.4 for SF up to 142 for the SF/BaTiO3 composite with 40 wt %, at room temperature and 1 kHz. Two relaxations processes are observed, the β-relaxation and the conductivity relaxation, both with temperature-dependent behaviour. The activation energy of the conductivity process decreases with increasing nanoparticle content and decreasing size. A Maxwell-Wagner-Sillar process related to the interface between the silk fibroin matrix and the BaTiO3 nanoparticles was also identified. [Display omitted] •Composites based on silk fibroin (SF) and ceramic nanoparticles (BaTiO3) have been developed.•The dielectric relaxation process is analyzed as a function of temperature and frequency.•The inclusion of BaTiO3 does not affect the morphology and vibrational bands of the polymer.•The dielectric values increase with increasing filler content and two relaxation processes are observed.•The tailorability of silk fibroin high ε′ is demonstrated for a new generation of advanced sustainable dielectric materials.