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Large Strain Response in <001> Textured 0.79BNT–0.20BKT–0.01NKN Lead-Free Piezoelectric Ceramics


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Templated grain growth (TGG) method was applied to fabricate textured lead-free piezoelectric ceramics 0.79Bi0.5Na0.5TiO3–0.20Bi0.5K0.5TiO3–0.01Na0.5K0.5NbO3 (0.79BNT–0.20BKT–0.01NKN) using plate-like Bi4Ti3O12 (BiT) grains, to improve its performances. Relationships between degree of orientation, microstructure, and piezoelectric properties of the textured ceramics were studied. Results showed that dense, c-axis (00l) textured 0.79BNT–0.20BKT–0.01NKN ceramics, with brick wall cross-sectional microstructures and strip-like grains aligned parallel to the tape casting direction, were obtained using this method. The highest degree of orientation (Lotgering factor = 94%) was achieved in samples with template content of 20 wt%. However, these samples did not exhibit enhanced strain response due to the composition deviation induced by the interdiffusion of BiT into the matrix composition. Instead, maximum strain value of 0.45% was observed in the textured sample with 5 wt% template, which was 50% higher than that of random ceramics and comparable with some PZT-based anti-ferroelectric ceramics, suggesting the textured ceramics could be a very promising lead-free piezoelectric material for application in electromechanical devices.