Microstructural, structural, dielectric, piezoelectric and energy storage properties of 0.2 wt% MnO2 doped (0.94-x)Na0.5Bi0.5TiO3–0.06BaTiO3-xK0.5Na0.5NbO3 ceramics (0 ≤ x ≤ 0.08)

Abstract

Lead free (0.94-x)Na0.5Bi0.5TiO3–0.06BaTiO3-xK0.5Na0.5NbO3 ceramics are under the spotlight owing to their multifunctional nature. We have systematically investigated the microstructural, structural, dielectric, piezoelectric and energy storage properties of the system in the range 0 ≤ x ≤ 0.08. There is a systematic reduction in grain size with increasing K0.5Na0.5NbO3(KNN) concentration. The enhancement in disorder with K0.5Na0.5NbO3(KNN) doping is evident from the increase in slope of the dielectric dispersion plots. The unpoled compositions have a cubic like structure in the whole range i.e. from x = 0 to x = 0.08. However, the application of electric field(poling) results in a structural transformation to lower symmetry upto x = 0.04. Beyond that the disorder dominates over the applied electric field and the structure is cubic like even in the poled state. The energy storage density increases from 0.08 J/cm3 for x = 0 to 1.19 J/cm3 for x = 0.05 and saturates thereafter. Discharge efficiency also follows a similar trend. The piezoresponse decreases with KNN doping from 151 pC/N for x = 0 to 4 pC/N for x = 0.08. It is observed that energy storage density and piezoresponse are complimentary properties which increase at the expense of each other.