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)-0.04SrTiO3 (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 (Smax/Emax = d33*) of 735 pm V−1 at 6 kV mm−1 was observed at room temperature. Interestingly, at a higher temperature of 110 °C, the sample still showed a large d33* of 570 pm V−1. Furthermore, the temperature-invariant electrostrictive coefficient for this sample was found to be 0.0285 m4 C−2 over the temperature range of 25-170 °C. Moreover, the energy density for x = 0.030 sample was ∼1.0 J cm−3 with an energy storage efficiency of ˃70% in the temperature range of 25-135 °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.