Giant electrostrain coefficient under low driving electric field in sodium potassium niobate piezoelectric ceramics with symmetrical bipolar strain.

Cao, Fuzhi; Cen, Zhenyong; Xu, Ze; Zhang, Xin; Shi, Xiaoming; Huang, Houbing; Liu, Zhaobo; Liu, Yi-Xuan et al. · Nat Commun · 2025

basic_science · Level V

Where this comes from

Abstract

Currently, achieving highly symmetrical bipolar strain and high electrostrain under low driving electric field remains challenging in piezoelectric materials. The designed potassium sodium niobate-based ceramics exhibit highly symmetrical bipolar strain and ultrahigh electrostrain coefficient (~2000 pm/V) under a low driving electric field of 8.4 kV/cm through A-site defect engineering and charge compensation. The highly symmetrical bipolar strain is related strongly to the lowly aligned defect dipoles by partially substituting A-site (Na<sup>+</sup>/K<sup>+</sup>) ions with Mn<sup>2+</sup>. The eye-catching performance is ascribed to the unique microstructure of atomic-scale polar nanoregions embedded in nano-domains (~34 nm) by tuning Na<sup>+</sup>/K<sup>+</sup> ions deficiency and coexistence of multiple phases. Phase-field simulations reveal that flattened energy barrier and multiphase nanodomains interplay to boost electrostrain at low driving fields. This work provides an innovative way of designing lead-free piezoelectric materials with highly symmetrical bipolar strain and giant electrostrain coefficient at low driving electric field, promising for high-precision actuators applications.