Dielectric and piezoelectric properties of modified lead-free NaNbO3–KNbO3/PVDF composite ceramics

Abstract

This work presents the results of study of the electrophysical properties of composite polymer ceramics (1[Formula: see text][KNN-LTSN]–[Formula: see text]PVDF at [Formula: see text] = 25 vol.% and [Formula: see text]= 50 vol.% in the temperature range of [Formula: see text] = 20–160[Formula: see text]C and frequency range of [Formula: see text] = 2 × 101–2 × 106 Hz. The concentration dependence of piezomodules of the studied materials has been analyzed as a function of temperature. X-ray measurements have also been carried out. A model of description of revealed dielectric parameters dispersion in the material is presented. The nonclassical modified Havriliak–Negami model written for complex electrical conductivity has been used to describe the temperature–frequency properties. It is shown that the dielectric spectra of the studied composites include three relaxation processes in the temperature ranges of 40–80[Formula: see text]C, 80–120[Formula: see text]C and 120–150 [Formula: see text]C, which were confirmed by the dynamics of changes in the dependences of [Formula: see text], tg[Formula: see text], [Formula: see text], [Formula: see text]([Formula: see text]) and [Formula: see text]([Formula: see text]. All three processes are almost exactly described by this model and well correlated with the studies by other researchers of the composites based on PVDF. The results of this work show that the use of such experimental model is suitable for describing the complex dielectric spectra of any nonlinear dielectrics including composite materials.