Dielectric and piezoelectric behavior of PVDF-modified 3-3 type cement-based piezoelectric composites

In this research, 3–3 type cement-based piezoelectric composites were prepared by casting Portland cement paste in porous lead zirconate titanate (PZT) ceramics, then the polyvinylidene fluoride (PVDF) of N-methylpyrrolidone solvent with concentration of 50–200 mg ml⁻¹ was utilized to modify the lead zirconate titanate-Potland cement (PZT-PC) composites. The effects of PVDF concentration on the density, microstructure, dielectric, piezoelectric and electromechanical properties were studied. The results indicate that the density of PZT-PC composites increased gradually with PVDF concentration for the increasing combined weight of PVDF with the composites. The introduction of PVDF has also contributed to the reduction of leakage current during the poling and testing process, which led to increased relative permittivity ϵ _r and longitudinal piezoelectric strain coefficient d ₃₃, while the dielectric loss tanδ and longitudinal piezoelectric voltage coefficient g ₃₃ demonstrated an opposite changing trend. The thickness electromechanical coupling factor K _t of composites increased with the concentration of PVDF solution. The acoustic impedance (Z) of PVDF modified PZT-PC composites ranged from 6.89 to 7.65 MRayls, making it suitable for applications in the health monitoring of civil engineering.