Microstructures and piezoelectric performance of eco-friendly composite films based on nanocellulose and barium titanate nanoparticle

Eco-friendly nanocellulose-based composite films including different barium titanate (BaTiO3) nanoparticle contents were fabricated by an efficient aqueous suspension casting and following electric poling. The microstructures, dielectric/electrical property, and piezoelectric performance of the nanocellulose composite films were investigated as a function of the BaTiO3 content. The electron microscopic images demonstrated that the BaTiO3 nanoparticles were uniformly dispersed in the nanocellulose-based composite films. The X-ray diffraction results confirmed the presence of piezoelectric tetragonal BaTiO3 nanoparticles in the nanocellulose matrix with cellulose II phase. The dielectric constant and loss tangent of the composite films were found to increase and decrease with increasing the BaTiO3 content, respectively, which is favorable to achieve high piezoelectric outputs. On the other hand, the piezoelectric performance of the composite films increased with the BaTiO3 content up to 40 wt% and it decreased for the composites with 50-60 wt% BaTiO3, which results from the trade-off effect between the piezoelectric performance and the mechanical stiffness of BaTiO3 nanoparticle. Accordingly, the nanocellulose composite film with 40 wt% BaTiO3 was found to attain maximum piezoelectric outputs of voltage of similar to 2.86 V, current of similar to 262.4 nA, and electric power of similar to 378.2 nW under a relatively low compressional stress of 5 kPa, which was high enough to charge microcapacitors after rectification.