Electromechanical properties of Nb doped 0.76Bi0.5Na0.5TiO3-0.24SrTiO3 ceramic

In this report, the piezoelectric, dielectric and ferroelectric characteristics of 0.76Bi(0.5)Na(0.5)TiO(3) (BNT)-0.24SrTiO(3) (ST) with niobium (Nb) (Nb-added BNT-24ST) ceramics synthesized by using a solid-state reaction are described. The X-ray diffraction analysis and field effect scanning electron microscopy of Nb-added BNT-24ST ceramics reveal the influence of Nb on the perovskite structure and suppression of grain growth within the composition range studied. The electromechanical properties of BNT-24ST ceramics were significantly increased up to 0.5 wt% Nb, and decreased with a further increased Nb content. Around the critical composition (0.5 wt% Nb) with an electric field of 5 kV mm(-1), a maximum strain (S-max) of 0.28% (d*33 similar to 605) at room temperature was obtained. Saturated polarization reached a maximum value of 27 mu C cm(-2) at a level of 0.5% Nb. The depolarization temperature moved to lower temperatures with Nb content and the peaks became more diffuse with an increasing content of Nb. Using a study of kinetic dynamics, the activation energy drop with 24ST and Nb-added 24ST is well explained by Vogel-Fulcher (VF) behavior and the Kolmogorov-Avrami-Ishibashi (KAI) model, which suggest that the B site vacancy generation in the perovskite structure has a reduction in energy barrier (E-a) with Nb addition. Increase of the phase transition region also occurred in Nb-added 24ST (>50 degrees C). This work indicated that this material can be considered as a suitable candidate material for high temperature, stable, lead free actuators.