Enhanced d33 value in (1 − x)[(K0.50Na0.50)0.97Li0.03Nb0.97Sb0.03O3] − xBaZrO3 lead-free ceramics with an orthorhombic–rhombohedral phase boundary

• A R–O phase boundary is identified in the compositional range of 0.04 ⩽ x ⩽ 0.06.
• An enhanced piezoelectric behavior is observed in the ceramic with x = 0.05.
• The R–O, Li and Sb, and higher εrPr are responsible for the enhanced d33.
• A piezoelectric behavior of d33 ∼ 235 pC/N and kp ∼ 0.44 is observed in such a ceramic.
• Such a material system is a promising lead-free piezoelectric candidate.

In this work, the rhombohedral–orthorhombic (R–O) phase boundary and the composition-induced piezoelectric properties have been observed in the (1 − x)[(K0.50Na0.50)0.97Li0.03Nb0.97Sb0.03O3] − xBaZrO3 [(1 − x)KNLNS − xBZ] lead-free ceramics prepared by the conventional solid-state method. Effects of BZ content on the phase structure, microstructure, and electrical properties of (1 − x)KNLNS − xBZ ceramics are studied. The R–O phase coexistence is found in these ceramics with the compositional range of 0.04 ⩽ x ⩽ 0.06, which is further confirmed by the XRD and the temperature dependence of the dielectric behavior. With increasing BZ content, their grains become smaller and much more uniform, the TO–T and TC drops, the remanent polarization decreases, and the dielectric constant increases. The ceramic with x = 0.05 has an enhanced piezoelectric behavior because of the involvement of R–O together with the addition of Li and Sb as well as a higher εrPr, and an optimum electrical behavior of d33 ∼ 235 pC/N, kp ∼ 0.44, 2Pr ∼ 42.0 μC/cm2, 2Ec ∼ 27.6 kV/cm, εr ∼ 1567, tan δ ∼ 3.3%, TC∼267 °C, TO–T ∼ 85 °C, and TR–O ∼ 5 °C is observed in such a ceramic, showing the material system is a promising lead-free piezoelectric candidate.