Dielectric and piezoelectric properties of lead free BZT-BCT/PVDF flexible composites for electronic applications

Abstract

In this study, a lead-free 0.50[Ba(Zr0.2Ti0.8)O3]0.50(Ba0.7Ca0.3)TiO3 (BZT-BCT) ferroelectric powder was prepared and used as a filler to fabricate 0–3 connectivity ceramic-polymer composites using polyvinylidene fluoride (PVDF) as the matrix in the development of flexible devices for electronic applications. Four composites with different weight fractions x(BZT-BCT)-(1−x)PVDF, where x=35, 45, 50, and 65 wt%, were prepared by employing melt mixing and a hot-pressing method. X-ray diffraction analysis showed the presence of ceramic (functional reinforcements) and polymer (matrix) phases in the composite material. Scanning electron microscopy images confirmed uniform dispersion of the ceramic filler in the PVDF matrix. Dielectric, ferroelectric, and piezoelectric analyses were carried out on the composite samples, the results of which are discussed in detail. The composite with x=65 wt% ceramic showed the highest dielectric constant (ε′) of 49 and a dielectric loss of 0.03 measured at a frequency of 1 kHz. In addition, the piezoelectric charge coefficient (d33) reached a maximum of 9 pC/Nwhen measured at 100 Hz after 24 h of sample poling when measured at room temperature. The relaxor behaviors of the composites are the same as that of pure PVDF and the ferroelectric polarization response of the composites is significantly influenced by the incorporation of BZT-BCT filler particles within the PVDF matrix. The experiment data were fitted to the theoretical equations, and modified Kerner, Yamada, and effective medium theory models were found to be useful for predicting the dielectric constant of the composites.