Large electrostrain achieved by the regulation of phase structure in Ba(Zr0.5Ti0.5)O3-Modified Bi0.5Na0.5TiO3–SrTiO3 lead-free ceramics
Herein, a series of lead-free ceramics, (1− x )(0.78Bi 0.5 Na 0.5 TiO 3 –0.22SrTiO 3 )– x Ba(Zr 0.5 Ti 0.5 )O 3 (abbreviated as BNST–BZT), were synthesized via the conventional solid-state reaction approach. The effects of introducing the BZT component on the electromechanical transformation properties and phase transition of BNST were thoroughly investigated, leading to the development of a corresponding phase diagram. The addition of BZT significantly influenced phase transitions and domain structures, with phase coexistence involving ferroelectric rhombohedral and relaxor tetragonal phases. XRD analysis and temperature-dependent measurements of dielectric and ferroelectric properties demonstrated that the relaxor phase content could be modulated by adjusting the BZT content and varying the temperature. Domain changes were also observed through PFM testing. With the addition of BZT, the RE-FE phase transition temperature T F-R is successfully adjusted to near room temperature, accompanied by the disruption of long-range ferroelectric domains and the formation of polar nanoregions. This transition marks a shift from NR to ER state. Specifically, with an optimized BZT content of 0.006, the material demonstrates a significant strain of 0.41 % under a 70 kV/cm and achieves a maximum normalized strain of 715 p.m./V at 50 kV/cm. This research introduces an effective doping strategy that offers valuable insights into the design and development of high-performance lead-free ceramics. Additionally, it investigates the mechanisms underlying the observed high strain responses, highlighting their potential application in lead-free piezoelectric actuators.
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