Preparation and characterization of low loss polyvinyl butyral/barium titanate nanocomposite films for energy storage applications

For energy storage applications, attaining high dielectric permittivity as well as low loss factor is the foremost target. This could be accomplished via filling polymer matrices with inorganic filler which is characterized by relatively high dielectric permittivity. In the present study, polyvinyl butyral (PVB) was used as a matrix material for preparing nanocomposite films filled with different weight fractions (2, 5, 10, and 15%) of barium titanate (BaTiO₃) using the casting approach. The results show that BaTiO₃ (BT) is well incorporated inside the PVB matrix. Although the dielectric permittivity has been decreased from 3.61 to 2.41 at 1 kHz upon filling the PVB matrix with 5 wt. % of BT, the PVB-BT-NPs-5 nanocomposite film shows the lowest loss factor ~ 0.0049, nearly half that for PVB, 0.0092, which implies the increased film ability to keep its stored energy. The PVB-BT-NPs-5 has been irradiated with gamma radiation to investigate its impact on the structure beside its dielectric and thermal properties. The crystallite size of BT has been decreased from 20.64 to 17.77 nm as PVB-BT-NPs-5 nanocomposite film has been irradiated at a dose of 0.5 kGy. The dielectric permittivity has been decreased from 2.41 to 2.37 at 1 kHz, whereas an increase from 0.0049 to 0.0073 in the loss factor is observed. Furthermore, the thermal stability has been decreased due to the deformation induced by gamma rays inside the nanocomposite films. Therefore, these nanocomposite films could be better exploited in energy storage applications in its un-irradiated form.