Phase structure and piezoelectric properties of NBT–KBT–BT ceramics prepared by sol–gel flame synthetic approach

• An antiferroelectric-like phase of NBT–KBT–BT ceramics exists at room temperature.
• The MPB of (1–2y)NBT–yKBT–yBT system ceramics lies in the composition of y = 0.05.
• A maximum d33 of about 213 pC/N was obtained in the 0.90NBT–0.05KBT–0.05BT ceramics.

Sol–gel flame synthetic approach was used to produce powders and the resultant ceramics of (Na0.5Bi0.5)TiO3–(K0.5Bi0.5)TiO3–BaTiO3 (NBT–KBT–BT) with different compositions. Detailed analysis of polarization–electric field (P–E) loops and strain–electric field (S–E) curves reveals that a tetragonal antiferroelectric-like phase exists at room temperature with a suitable composition. Because of the morphotropic phase boundary (MPB) behavior, the maximum piezoelectric constant d33 of about 213 pC/N with an electromechanical coupling factor kp of about 29% and a remnant polarization Pr of 23.55 μC/cm2 were obtained in the 0.90NBT–0.05KBT–0.05BT ceramics. This work provides new insight to further optimized lead-free NBT–KBT–BT piezoelectric ceramics for practical use in different composition ranges at room temperature.