Phase Transition, Electrical Properties, and Temperature‐Insensitive Large Strain in BiAlO₃‐Modified Bi_0.5(Na_0.75K_0.25)_0.5TiO₃ Lead‐Free Piezoelectric Ceramics

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.

Comparative study of the polarization and strain of inclusion-type and layer-type 0.94Bi(NaK)TiO3–0.06BiAlO3/Bi(NaK)TiO3 ceramic composites

“…The XRD patterns of all the ceramics indicated a pure perovskite structure without secondary phases. According to previous studies [16,24,25], the BNKTeBA exhibited the mixed state of psuedo-cubic and tetragonal phases. Meanwhile, the BNKT showed the tetragonal phase.…”

Electrical properties and low temperature sintering of BiAlO3 doped (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 lead-free piezoelectric ceramics

“…This phase transformation can be explained using the tolerance factor proposed by Goldschmidt et al The tolerance factor t is calculated using the formula [17],…”

Tailoring ergodicity through selective A-site doping in the Bi1/2Na1/2TiO3–Bi1/2K1/2TiO3 system

“…6,7 Several reports have focused on modifying the system through solid solutions achieving promising large signal strain properties, namely, d 33 * above 500 pm/V at 6 kV/mm. [8][9][10][11][12] Other studies focused on either A-and/or B-site doping to improve small and large signal electromechanical properties. [13][14][15][16] It was proved that either replacing Bi on the A-site 16 or all A-site cations are effective approaches.…”