High piezoelectric and dielectric constant of Fe/In Co‐doped KNN‐based ceramics regulated by lattice distortion

Abstract The new (0.96‐ x )(K _0.48 Na _0.52 Nb _0.96 Sb _0.04 )O ₃ ‐0.04(Bi _0.5 Ag _0.5 )ZrO ₃ ‐ x (Fe ₂ O ₃ ‐In ₂ O ₃ ) ceramics with high dielectric, and electromechanical coupling properties were designed. In this work, the effect of KNN‐based ceramics lattice distortion (c/a) and microstructure on the electrical properties was explored by varying the doping amount of Fe ³⁺ and In ³⁺ . The problem of a large number of oxygen vacancies generated by the volatilization of K and Na can be well solved by introducing Fe ³⁺ and In ³⁺ . The bulk density increases significantly and the maximum value is about 4.52 g/cm ³ .The sample with x = 0.003 has the smallest c/a, and exhibits the best piezoelectric and dielectric properties ( d ₃₃ = 536 pC/N, ε _r = 3432 and k _p = 55.8 %). Low doping concentration of Fe ₂ O ₃ is considered a “soft” addition for KNN‐based piezoelectric ceramics. The study of this mechanism provides a new idea to regulate the electrical performance of KNN‐based ceramics.