Effect of a lattice distortion strategy on the phase transition and properties in KNN‐based ceramics

Abstract

High performance lead‐free piezoelectric ceramics are of great importance to the sustainable development of the environment. To obtain excellent comprehensive performance KNN‐based lead‐free piezoelectric ceramics, a lattice distortion strategy combined with domain configuration was designed in (1 −  x)K _0.5Na _0.5Nb _0.95Sb _0.05O ₃– xCaHfO ₃ ((1 −  x)KNNS– xCH) system by introduced Ca ²⁺ into the A‐site and Hf ⁴⁺ into the B‐site. The results demonstrated that the rhombohedral–orthorhombic–tetragonal polymorphic phase boundary (PPB) was constructed in 0.02 ≤  x ≤ 0.04 and significant lattice distortion occurred in R‐ and T‐phase. Moreover, the 0.97KNNS–0.03CH sample exhibited excellent electrical performance (e.g., k _p ∼ 43.8%, d ^* ₃₃ ∼ 478.6 pm/V, and d ₃₃ ∼ 392 pC/N) together with a high Curie temperature ( T _C ∼ 295°C) profited from the PPB and domain configurations. The ceramics also showed the optimal thermal stability, which was beneficial to promote the development of KNN‐based ceramics.