Dielectric and piezoelectric properties of (K0.475Na0.495Li0.03) NbO3-0.003ZrO2/PVDF 0–3 composite reinforced with two types of nano-ZnO particles

(K 0.475 Na 0.495 Li 0.03 ) NbO 3 –0.003ZrO 2 (KNNL-Z) ceramic was synthesized by the conventional solid-state reaction method. The purchased ZnO nanorods (denoted as ZnO1) and synthesized ZnO nanocakes (denoted as ZnO2) were used in the preparation of two types of composites fabricated by hot-pressing process using KNNL-Z ceramic powder, two kinds of ZnO nanoparticles, and PVDF polymer. The effects of the ZnO nanoparticles on the crystalline structures, morphology, thermal, dielectric, and piezoelectric properties of the composites were studied systemically. The KNNL-Z ceramic possesses a perovskite-type orthorhombic phase and the PVDF polymer mainly possesses α , β , and γ phases. Two kinds of ZnO all possess hexagonal wurtzite structures without any impurity phase. Interestingly, the incorporation of the ZnO nanoparticles has great impact on lattice constants and strain. In addition, the β phase content increases when the ZnO nanoparticles are added. From differential scanning calorimetry (DSC) measurements, it is found that the ZnO nanoparticles can enhance the thermal stability of composites. Moreover, the dielectric and piezoelectric properties are also found to be improved with the increase of ZnO content. Especially when 10 wt% ZnO2 is added, the dielectric constant reaches the value of 469.4 (100 Hz) at room temperature and the piezoelectric coefficient is 55 pC/N. After 30 days of aging test, it is obvious that all the composites present a good stability of piezoelectric property.