High-throughput synthesis and electrical properties of BNT–BT–KNN lead-free piezoelectric ceramics

A lead-free piezoelectric ceramic library of (1 − x − y)Bi0.5Na0.5TiO3–xBaTiO3–yK0.5Na0.5NbO3 [100(1 − x − y)BNT–100xBT–100yKNN] (0 ≤ x ≤ 0.12, 0 ≤ y ≤ 0.12) with 91 samples was prepared by using a high-throughput (HT) method. By comparing the performance mapping of Pr, Ec, TF–R, d33, d33* and the domain configuration to the compositions, the property diagram of the ternary library could be identified with three regions of (I) rhombohedral ferroelectric, (II) relaxor ferroelectric and (III) tetragonal ferroelectric phases. Remarkable phase-boundary effects were observed between two adjacent regions with phase coexistence features. Interestingly, the maximum d33 value was obtained near the I–III region boundary, while the maximum d33* value was obtained on the I–II region boundary. The electric field-induced rhombohedral–tetragonal phase transition at the I–III region boundary brings good piezoelectric properties. The reversible relaxor–ferroelectric phase transition near the I–II region boundary could be the origin of the enhanced depolarization effect of the samples with the recovery of the electric field, leading to high d33* values.