Synergistic Domain and Defect Engineering Enables Giant Electrostrain With High Piezoelectric Sensitivity in...

Achieving both high piezoelectric sensitivity and large electrostrain in lead-free ceramics remains a challenge due to inherent trade-offs between polarization stability and mobility. Prior research has shown that these properties often compete, limiting performance in lead-free systems. While lead-based materials like PZT offer superior electromechanical responses, environmental concerns have driven efforts to develop lead-free alternatives. However, the lack of a design framework that coordinates domain structure and defect chemistry has hindered progress. This gap motivated the current study to explore a new paradigm for enhancing both properties simultaneously. The researchers propose that hierarchical domain structures and defect-induced internal fields could offer a solution. Existing methods have focused on single-parameter tuning, but this paper introduces a multifunctional strategy. The study builds on prior findings about defect mediation and domain architecture in ferroelectrics. By addressing these limitations, the work aims to advance the field of lead-free piezoelectrics.

The aim of this study is to develop a lead-free piezoelectric ceramic with both high piezoelectric sensitivity and large electrostrain. The specific problem addressed is the inherent trade-off between polarization stability and mobility in lead-free materials. The motivation stems from the need for environmentally friendly alternatives to lead-based ceramics like PZT. The researchers propose that combining domain engineering with defect chemistry could overcome this limitation. The study focuses on KNN-based ceramics, a promising lead-free system. The goal is to identify a design strategy that enables simultaneous enhancement of piezoelectric and electrostrain responses. The approach involves using Sb⁵⁺ substitution as a multifunctional parameter. The study tests whether this method can stabilize hierarchical domains and introduce internal bias fields to improve performance.

The study uses (K_0.5Na_0.5)NbO₃ (KNN)-based ceramics as a model system. A partial substitution of Nb⁵⁺ with Sb⁵⁺ is introduced to modulate phase constitution, domain architecture, and defect chemistry. The material is doped with Bi_0.5Li_0.5HfO₃ to enhance performance. Structural and domain configurations are analyzed using X-ray diffraction and scanning electron microscopy. Polarization behavior is studied through electric field cycling and hysteresis measurements. Defect chemistry is probed using electron paramagnetic resonance and density functional theory calculations. The researchers assess electrostrain under applied electric fields. The study evaluates the piezoelectric coefficient and strain response at optimal Sb⁵⁺ concentrations. The approach integrates domain engineering with defect-mediated internal bias fields to achieve the desired electromechanical properties.

At an optimal Sb⁵⁺ concentration, the ceramics exhibit a piezoelectric coefficient of approximately 350 pC N^-1. The material achieves an electrostrain of about 1.14%, among the highest reported for lead-free systems. Hierarchical multivariant domain configurations are stabilized through Sb⁵⁺ substitution. Aligned defect dipoles associated with A-site and oxygen vacancies create energetic asymmetry in polarization. This asymmetry enables low-barrier polarization rotation and reversible domain switching. The internal bias fields reduce the energy required for polarization reorientation. The material's performance is attributed to the cooperative regulation of domain structures and defects. The results demonstrate that the design strategy successfully overcomes the trade-off between sensitivity and strain.

The authors propose that the cooperative regulation of domain structures and defect chemistry provides a general design paradigm for lead-free piezoelectrics. The study shows that Sb⁵⁺ substitution acts as a multifunctional parameter to enhance performance. The optimized material achieves high piezoelectric sensitivity and electrostrain simultaneously. The results suggest that this approach can be transferred to other lead-free systems. The work addresses a fundamental challenge in the field of piezoelectric ceramics. The findings support the idea that hierarchical domain configurations and defect dipoles are essential for improving electromechanical responses. The study does not claim that this is the only solution but proposes a viable strategy. The authors suggest that this method could guide future developments in lead-free piezoelectrics.