Various lead-free (K x Na 1Àx ) 0.98 Li 0.02 (Nb 0.82Ày Ta 0.18 Sb y )O 3 ceramics with x 5 0.50, y 5 0.00-0.07 or x 5 0.40-0.60, y 5 0.05 were prepared by the conventional solid-state reaction method. Systematic investigation on the microstructures, crystalline structures, and dielectric and piezoelectric properties was carried out. Remarkably strong piezoelectricity has been achieved in (K 0.45 Na 0.55 ) 0.98 Li 0.02 (Nb 0.77 Ta 0.18 Sb 0.05 )O 3 ceramic, which shows the excellent piezoelectric properties of d 33 5 413 pC/N, d 31 5 À153 pC/N, k p 5 0.50, and k 33 5 0.62. It is considered that the observed strong piezoelectricity should be ascribed to several combined decisive factors, such as the phase coexistence due to an orthorhombic-tetragonal polymorphic phase transition near room temperature, the high electronegativity of Sb 51 ions as compared with those of Nb 51 ions and Ta 51 ions, and the relatively ideal microstructure with high density, large average grain size and narrow grain-size distribution.

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