Giant strain response with low hysteresis in potassium sodium niobate based lead-free ceramics

In this work, the relationships between the composition-driven phase boundary, ferroelectricity and strain properties of the (1-x)(K0.48Na0.52)(Nb1-ySby)O3-xBi0.5(Na0.82K0.18)0.5ZrO3 (abbreviated as (1-x)KNN1-ySy-xBNKZ) ceramics were investigated. A giant electric field-induced strain of 0.3% (d33∗ = 750 p.m./V) and a low hysteresis (16.4%) were obtained in the 0.97KNN0.98S0.02-0.03BNKZ ceramics. The giant strain is attributed to the enhanced piezoelectricity induced by the appearance of the O-T phase boundary and the electric-field-induced phase transition from the relaxor phase to the ferroelectric phase. Furthermore, the 0.97KNN0.98S0.02-0.03BNKZ ceramics exhibit good thermal stability in the temperature range from 25 °C to 150 °C. Hence, this work can promote the practical applications of KNN-based lead-free piezoelectric ceramics in highly sensitive and precise piezoelectric actuators.