Dielectric Relaxation in K 0.5 Na 0.5 NbO 3 -PVDF Composites.

K 1- x Na x NbO 3 is considered as an alternative system for lead-based functional ceramics widely used in transducers, sensors and actuators. In some applications however, the composites of electroactive ceramic and polymer, with low acoustic impedance and dielectric permittivity that can be tailored to various requirement, are more useful. We studied dielectric relaxation processes in polyvinylidene fluoride (PVDF) loaded with K 0.5 Na 0.5 NbO 3 powder in wide temperature and frequency range. The powder was prepared by solid state synthesis and characterized by HRTEM and NIR Raman spectroscopy. The dielectric response of (K 0.5 Na 0.5 NbO 3 ) 0.32 (PVDF) 0.68 composite, of (0–3) connectivity, was found to be determined by the relaxation processes of the polymer matrix with an additional broad low-frequency anomaly at ∼⃒ 305 K that we relate to a response of water absorbed by the shell of KNN grains. [ABSTRACT FROM AUTHOR]