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)

Lead free (0.94-x)Na 0.5 Bi 0.5 TiO 3 –0.06BaTiO 3 -xK 0.5 Na 0.5 NbO 3 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 K 0.5 Na 0.5 NbO 3 (KNN) concentration. The enhancement in disorder with K 0.5 Na 0.5 NbO 3 (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/cm 3 for x = 0 to 1.19 J/cm 3 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.