Design of highly active and stable (K0.48Na0.48Li0.04)(Nb0.975Sb0.025)O3–(Bi0.5Na0.5)(Zr0.8Ti0.2)O3 lead–free piezoelectric ceramics by constructing rhombohedral–tetragonal phase boundaries at room temperature

Traditional piezoelectric materials cause serious environmental and health issues because of their lead–containing substances, and thus lead–free piezoelectric ceramics would have many applications. In this study, we successfully prepared the lead–free ceramics (1- x ) (K 0 · 48 Na 0 · 48 Li 0.04 ) (Nb 0 · 975 Sb 0.025 )O 3 – x (Bi 0 · 5 Na 0.5 ) (Zr 0 · 8 Ti 0.2 )O 3 ((1- x )KNLNS– x BNZT, x = 0, 0.005, 0.0075, 0.01, 0.015, 0.02 and 0.03) with rhombohedral–tetragonal (R–T) phase coexistence near room temperature, employing con–entional solid sintering. The minimum cell volume of the ceramics and R–T phase coexistence in them were achieved at a doping amount x = 0.01, which facilitated the optimal performance of the ceramics ( d 33 ∼467 pC/N ± 14 pC/N, T c∼272 °C, ε r ∼1676, k p ∼0.42, where d 33 : piezoelectric constant; T c: Curie temperature ; ε r : dielectric constant; k p : electromechanical coefficient). The ceramics exhibited microstructures with high density and low porosity and had a maximum relative density of 95.68 %. At x = 0.01, the ceramics exhibited a uniformly distributed small domain structures with nanodomains, accounting for their high-voltage electrical properties. Because these stable and reliable piezoelectric (1- x )KNLNS– x BNZT ceramics exhibit excellent electrical performance, they can replace lead–based materials. The direct solid–phase sintering method provides prospects for the large–scale application of the lead–free piezoelectric ceramics.