Sharpening polycrystalline phase boundary for potassium sodium niobate ceramics with MnF₂ modification

Abstract

The influence of anion on structure and performance is unclear in potassium sodium niobate ((K,Na)NbO3; KNN)‐based ceramics, while cation doping has been widely researched. Here, the phase structure and electrical properties are explored in MnF2‐doped KNN ceramics. Significantly, sharp rhombohedral–orthorhombic (R–O) and orthorhombic–tetragonal (O–T) phase boundary as well as reduced diffusion degree is exhibited in the ceramics along with little changed phase transition temperatures due to the optimized F− content at O site, which is different from that of cation replacement for A and B sites. Notably, the domain wall motion is facilitated due to the increased A vacancy and decreased O vacancy along with strengthened polarity, originating from the higher valence state and electronegativity of F− with respect to O2−. And then, enhanced ferroelectricity is realized via MnF2 modification, the piezoelectricity is elevated in turn. This work presents a new idea of anion doping for controlling structure and properties in perovskite materials.

Hardening Effect on the Electromechanical Properties of KNN-Based Ceramics Using a Composite Approach

“…The reduction in grain size can also be attributed to a reduction in oxygen vacancies. 30,31 The reduction in grain size can have the effect of constraining the domain wall motion and dielectric response, which has an impact on the electrical properties of composites. 32 The two-dimensional elemental mapping of the composites is shown in Figures 4e and S1 (in the Supporting Information) for more intuitive verification of the formation of the KNNT-BNZ-BFO/xKCN composites.…”

Excellent power generation and enhanced mechanical properties in PPT-structured Pb-free piezoceramics with ZrO2 inclusions

“…It is believed that the long-range ordering of the ferroelectric matrix is broken by the aliovalent dopant ions Bi 3+ and Zr 4+ in BNZ, preventing the formation of ordered macro-domains. 31 Besides, due to the differences in thermal expansion coefficient a and elastic modulus E between the KNN-based ceramics and ZrO 2 , heterogeneous interfacial stress would be generated during the cooling stage of ceramic sintering. 23 Fig.…”

Facilitated reversible domain switching at multiphase boundary in periodically orthogonal poled KNN‐based ceramics: Strain versus non‐180o domain

“…[2][3][4][5] Potassium sodium niobate (KNN)-based materials, as promising lead-free candidates, have occupied the largest market share (37.2%) in the lead-free piezoelectric ceramics owing to their high Curie temperature and excellent electric properties. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] Unfortunately, they still suffer from poor strain compared to that of the shape memory alloys (SMAs) and giant magnetostrictive materials (Terfenol-D). 21,22 Therefore, it is necessary to urgently develop KNN-based lead-free materials with excellent strain.…”

“…Recently, the demand for sustainable development has motivated researchers and industry to boost the development of lead‐free alternatives 2–5 . Potassium sodium niobate (KNN)‐based materials, as promising lead‐free candidates, have occupied the largest market share (37.2%) in the lead‐free piezoelectric ceramics owing to their high Curie temperature and excellent electric properties 6–20 . Unfortunately, they still suffer from poor strain compared to that of the shape memory alloys (SMAs) and giant magnetostrictive materials (Terfenol‐D) 21,22 .…”