Unveiling the Adjustable Electromechanical Properties in (1- x )Bi _0.5 Na _0.5 TiO ₃ - x (BiNaBaSrZn) _0.2 TiO ₃ Composite System through High-Entropy Strategy

Bi 0.5 Na 0.5 TiO 3 (BNT) with a perovskite structure is regarded as one of the important lead-free candidates for future electromechanical devices due to its intrinsic relaxation. The enhancement of electromechanical properties, such as the piezoelectric coefficient (d 33 ) and planar electromechanical coupling factor ( k p ), is expected by constructing and regulating the relaxor boundaries in the BNT. However, the correlation still needs to be further investigated between the electromechanical properties and the induced comprehensive effects during the construction process of relaxor boundaries. High-entropy strategy is undoubtedly another window for exploring the structure-performance physical relationship between relaxation and electromechanical properties, due to the multidimensional effects such as strong disorder, distinct lattice distortion, and slow diffusion. This study quantitatively introduces the high-entropy component of (BiNaBaSrZn) 0.2 TiO 3 into the conventional ferroelectric BNT matrix to effectively regulate the microstructure, morphology, and electromechanical properties. Incorporating a high-entropy component evidently improves the degree of disorder, accompanied by the gradual evolution process of rhombohedral → rhombohedral/tetragonal → rhombohedral phase. Moreover, with a high-entropy ratio at 30%, the values of room-temperature d 33 and k p, respectively, reach 122 pC/N and 0.434, which are ∼1.5 and ∼1.9 times that of the BNT parent. This work probes the modulation of electromechanical properties in BNT-based materials from an additional perspective of high-entropy strategy, providing more methods for performance enhancement of lead-free dielectrics and laying an experimental foundation for designing the BNT-based electromechanical materials.