Design of highly active and stable(K 0.48 Na 0.48 Li 0.04 )(Nb 0.975 Sb 0.025 ) O 3-(Bi 0.5 Na 0.5 )(Zr 0.8 Ti 0.2 )O 3 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 & sdot;48 Na 0 & sdot;48 Li 0.04 ) (Nb 0 & sdot;975 Sb 0.025 )O 3 - x (Bi 0 & sdot;5 Na 0.5 ) (Zr 0 & sdot;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 degrees C, epsilon r -1676, k p -0.42, where d 33 : piezoelectric constant; T c: Curie temperature; epsilon 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.