Abstract Lead-free (Na 0.5 K 0.5 )NbO 3 -based piezoelectric ceramics were successfully fabricated by substituting with a small amount of BiFeO 3 (BF). Difficulty in sintering of pure NKN ceramics can be eased by adding a few molar percent of BF, and the crystalline structure is also changed, leading to a morphotropic phase boundary (MPB) between ferroelectric orthorhombic and rhombohedral phases. The MPB exists near the 1–2 mol% BF-substituted NKN compositions, exhibiting enhanced ferroelectric, piezoelectric, and electromechanical properties of P r =23.3 μC/cm 2 , d 33 =185 pC/N, and k p =46%, compared to an ordinarily sintered pure NKN ceramics. The MPB composition has a Curie temperature of ∼370 °C, comparable to that of some commercial PZT materials.