High strain response and low hysteresis in BaZrO₃-modified KNN-based lead-free relaxor ceramics

The high driving electric field and the large strain hysteresis are subject to a challenge for piezoelectric actuators’ practical applications. In order to obtain the piezoceramics with giant strain and low hysteresis at small electric field, a ternary solid solution (0.97-x)(K_0.48Na_0.52)Nb_0.965Sb_0.035–0.03Bi_0.5(K_0.18Na_0.82)_0.5ZrO₃-xBaZrO₃ (x = 0–0.06) was designed and synthesized by the traditional solid-state reaction method. The relationships among phase transition, microstructure, and electrical properties of the ceramics samples were systemically investigated. Under a low electric field of 4 kV/mm, the ceramic with x = 0.02 obtained a high bipolar strain of 0.29% (S_max/E_max = 729 pm/V) and a low hysteresis of 13.8%. The excellent piezoelectric properties are mainly attributed to rhombohedral–orthorhombic–tetragonal (R–O–T) phase boundary and the relaxor-to-ferroelectric phase transition. We believe that our research can not only provide the pathway of achieving KNN-based ceramics with high strain and low hysteresis but also promote the practical application of lead-free piezoelectric actuators.