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Phase Transition, Electrical Properties, and Temperature-Insensitive Large Strain in BiAlO3-Modified Bi0.5(Na0.75K0.25)0.5TiO3 Lead-Free Piezoelectric Ceramics

Authors


  • E. Suvaci–contributing editor

Author to whom correspondence should be addressed: e-mail: kimiw@mail.ulsan.ac.kr

Abstract

Lead-free piezoelectric (1–x)(Bi0.5(Na0.75K0.25)0.5TiO3)-xBiAlO3 (BNKT25-xBA, x = 0–0.100) ceramics were synthesized using a conventional solid-state reaction method. The effect of BA addition into the BNKT25 ceramics was investigated by X-ray diffraction, dielectric and ferroelectric characterizations, and electric field-induced strain. X-ray diffraction revealed a phase transition from a tetragonal to a pseudocubic phase at x = 0.050. As the BA content increased, the maximum dielectric constant as well as the depolarization temperature (Td) decreased. The polarization and strain hysteresis loops indicate that the addition of BA significantly disrupts the ferroelectric order of the BNKT25 ceramics leading to a degradation of the remanent polarization and coercive field. However, the destabilization of the ferroelectric order is accompanied by a significant enhancement in the unipolar strain which peaks at x = 0.025 with a value of ~0.29%, which corresponds to a normalized strain, d*33 (=Smax/Emax) of 484 pm/V. It was observed that the unipolar strain of 0.025xBA is fairly temperature-insensitive up to 150°C, even at 130°C the d*33 is as large as ~415 pm/V.

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