Enhanced bipolar fatigue resistance in BaZrO3-modified (K,Na)NbO3 lead-free piezoceramics

0.92(K0.5Na0.5)NbO3-0.02(Bi0.8Li0.2)TiO3-0.06BaZrO(3) (BZ6) is a lead-free piezoelectric ceramic with excellent piezoelectric performance (such as the normalized strain d(33)*reaches up to 476 pm/V). Considering potential device applications, it is essential to evaluate the ceramic's resistance to electrical fatigue. The bipolar fatigue behavior of (K,Na)NbO3 (KNN)-based lead-free piezoelectric ceramics was investigated. Comparative analysis shows that BaZrO3-modified KNN ceramics have strong resistance to bipolar fatigue due to the coexistence of rhombohedral and tetragonal phase and the depinning of domain walls, whereas microstructural damage under mechanical stress makes pristine KNN ceramics susceptible to bipolar cycling. The hypothesis was systematically verified through the study of cycle-dependent small and large signal parameters and microscopic morphology. Our findings can guide the future design of KNN compositions with high resistance to bipolar fatigue.