Investigating the effect of nano SnO2 on the electrical properties of KNN/PVDF-HFP piezoelectric composite

In recent years, piezoelectric materials have received great attention due to their wide applications in transducers, actuators, and sensors. In the meantime, lead-based piezoelectric materials have become the most successful piezoelectric materials in practical applications due to their excellent electrical properties, but due to the toxicity of lead and its harms to human health and the environment, their use has been limited. Among lead-free piezoelectric compounds, potassium-sodium niobate compound (KNN) has shown promising dielectric, ferroelectric and piezoelectric properties. KNN-ZnO ceramic compound with high density (ρth=95%), favorable microstructure, suitable dielectric and piezoelectric properties (K=875.12, d33=125pC/N, D=0.01) was chosen as the ceramic phase for composite fabrication. On the other hand, polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) polymer with favorable piezoelectric and mechanical properties was selected as the polymer phase. To achieve special properties of the composition, ceramic-polymer composites were made, and the electrical behavior of these composites was evaluated. In this research, the cold sintering process was used to make KNN-ZnO/PVDF-HFP composites and the effect of adding different amounts of nano SnO2 on the final properties of the composites was investigated. According to the results, adding small amounts of SnO2 to the composite containing 80% by weight of KNN-ZnO increased the density and dielectric constant of the composite, but there were no specific changes in the piezoelectric properties of the composite. Among the composite samples, the sample with 1wt% of nano tin oxide had the highest values ​​of voltage coefficient and figure of merit