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)K0.5Na0.5Nb0.95Sb0.05O3–xCaHfO3 ((1 − x)KNNS–xCH) system by introduced Ca2+ into the A‐site and Hf4+ 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., kp ∼ 43.8%, d*33 ∼ 478.6 pm/V, and d33 ∼ 392 pC/N) together with a high Curie temperature (TC ∼ 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.

Ultrafast charge‐discharge and enhanced energy storage properties of lead‐free K0.5Na0.5NbO3‐based ceramics

“…The PFM images can reflect the local phenomena of domain structures, although it is still reasonable to explain the domain switching dynamic behavior and the domain variation of KNN-0.030CB ceramics by microscopic reversible transition during the processes of voltage application and removal. 40 As is exhibited in the amplitude and phase images there are no normal ferroelectric domains in KNN-0.030CB ceramics, but nanoscale domains (Figure 5A1,A2). Since the host Na + and K + are replaced by the substitution of Bi and Ce ions at the A-site, the long-range ordered ferroelectric domains are decomposed and random fields are introduced, also the substitution of Bi and Ce ions emerge PNRs, part of these PNRs will merge and become percolation clusters, and these percolation clusters will then turn into nanodomains.…”

“…Since the host Na + and K + are replaced by the substitution of Bi and Ce ions at the A-site, the long-range ordered ferroelectric domains are decomposed and random fields are introduced, also the substitution of Bi and Ce ions emerge PNRs, part of these PNRs will merge and become percolation clusters, and these percolation clusters will then turn into nanodomains. 40 In general, the substitution of Bi and Ce ions may cause the destruction of the long-range ordering and the formation of nanodomains. In addition, grain size is directly related to domain size, and the refinement of grain size will contribute to the refinement of domains.…”

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

“…Lv found a large number of parallel striped domains in ceramics with high T‐phase and interpreted them as large c/a 25 . In addition to this, c/a influence on the electrical properties of ceramics has been proposed by other researchers, 26–29 but its mechanism has not been reported in detail 19,30,31 …”

“…25 In addition to this, c/a influence on the electrical properties of ceramics has been proposed by other researchers, [26][27][28][29] but its mechanism has not been reported in detail. 19,30,31 (Bi, Ag)ZrO 3 (BAZ) has been widely used to construct nanodomain structures to improve the piezoelectric performance of KNN-based ceramics. KNN-BAZ ceramics are rhombohedral-orthorhombic-tetragonal (R-O-T) phase coexisting with piezoelectric coefficient (d 33 ) and relative dielectric constant (ε r ) of 347 pC/N and 1200, respectively.…”

Decoding the Piezo-Contributions of Potassium Sodium Niobate Ceramics

“…A series of research advancements in enhancing the performance of KNN-based ceramics have been studied by doping to create phase boundaries near room temperature. − They have also utilized various characterization methods to conduct structural analysis and investigate the underlying physical mechanisms. In the realm of piezoelectric ceramics, their piezoelectric activity is typically a combination of both intrinsic and extrinsic piezoelectric contributions. ,− The intrinsic contribution to the piezoelectric response refers to the linear piezoelectric effect associated with lattice displacement, primarily dependent on lattice distortion, which is a reversible response. The extrinsic contribution mainly arises from domain motion, including domain wall vibration, domain switching, and domain wall movement, which can be both irreversible and reversible.…”