Superior Large-Signal Piezoelectric Coefficient in Textured NBT-Based Piezoceramics by Template-Induced Structure and Composition Modulation.

Abstract

The field-induced-phase transition in (Na1/2Bi1/2)TiO3-based lead-free piezoceramics can be facilitated in the ⟨001⟩-crystallographic orientation, and the templated grain growth is an effective method to align polycrystalline ceramics along with specific directions. However, due to the low texturing degree and undesirable composite effect of the added templates, the textured ceramics using the templated grain growth (TGG) method usually require a higher driving field to trigger the phase transition instead. Here, ⟨001⟩-textured (Na0.5Bi0.5)0.935Ba0.065Ti0.978(Fe0.5Nb0.5)0.022O3 ceramics are prepared through a liquid-phase-assisted TGG process at a low sintering temperature (1000 °C), in which the NaNbO3 (NN) templates induce a strong crystallographic anisotropic structure (a high Lotgering factor of 95%) while dissolving into oriented grains. The dissolution of templates acts as a composition doping and contributes to reducing the driving electric field as proven by the phase-field simulation analysis. Furthermore, electrical and structural characterizations reveal that an increased ionic disorder occurs in the textured ceramic, causing highly dynamic polar nanoregions and a larger reversible phase transition. Thanks to the appropriate structure/composition control, the textured ceramic achieves a large d33* value of 907 pm/V at 40 kV/cm. The high-performance lead-free ceramic under low driving electric field benefits the development of multilayer piezoelectric actuators.