Thermal-stability of electric field-induced strain and energy storage density in Nb-doped BNKT-ST piezoceramics

In this work, the relationship between the structural mechanisms and macroscopic electrical properties of the Nb-modified 0.96(Bi0.5Na0.84K0.16TiO3)-0.04SrTiO(3) (BNKT-ST) system were elucidated by using temperature dependent and in situ synchrotron X-ray diffraction (XRD) techniques. For the composition x = 0.0175, a large signal piezoelectric coefficient (S-max/E-mnx = d(33)(star)) of 735 pm V-1 at 6 kV mm(-1) was observed at room temperature. Interestingly, at a higher temperature of 110 degrees C, the sample still showed a large d(33)(star) of 570 pm V-1. Furthermore, the temperature-invariant electrostrictive coefficient for this sample was found to be 0.0285 m(4) C-2 over the temperature range of 25-170 degrees C. Moreover, the energy density for x = 0.030 sample was similar to 1.0 J cm(-3) with an energy storage efficiency of 70% in the temperature range of 25-135 degrees C. These results suggest that the synthesized Nb-modified BNKT-ST system is promising for the design of ceramic actuators as well as capacitor applications.