Effect of uniaxial stress on ferroelectric behavior of (Bi1/2Na1/2)TiO3-based lead-free piezoelectric ceramics

Abstract

Prior studies have shown that a field-induced ferroelectricity in ceramics with general chemical formula (1−x−y)(Bi1/2Na1/2)TiO3-xBaTiO3-y(K0.5Na0.5)NbO3 and a very low remanent strain can produce very large piezoelectric strains. Here we show that both the longitudinal and transverse strains gradually change with applied electric fields even during the transition from the nonferroelectric to the ferroelectric state, in contrast to known Pb-containing antiferroelectrics. Hence, the volume change and, in turn, the phase transition can be affected using uniaxial compressive stresses, and the effect on ferroelectricity can thus be assessed. It is found that the 0.94(Bi1/2Na1/2)TiO3-0.05BaTiO3-0.01(K0.5Na0.5)NbO3ceramic (largely ferroelectric), with a rhombohedral R3c symmetry, displays large ferroelectric domains, significant ferroelastic deformation, and large remanent electrical polarizations even at a 250 MPa compressive stress. In comparison, the 0.91(Bi1/2Na1/2)TiO3-0.07BaTiO3-0.02(K0.5Na0.5)NbO3ceramic (largely nonferroelectric) possesses characteristics of a relaxor ferroelectricceramic, including a pseudocubic structure, limited ferroelastic deformation, and low remanent polarization. The results are discussed with respect of the proposed antiferroelectric nature of the nonferroelectric state. Prior studies have shown that a field-induced ferroelectricity in ceramics with general chemical formula ͑1−x − y͒͑Bi 1/2 Na 1/2 ͒TiO 3 -xBaTiO 3 -y͑K 0.5 Na 0.5 ͒NbO 3 and a very low remanent strain can produce very large piezoelectric strains. Here we show that both the longitudinal and transverse strains gradually change with applied electric fields even during the transition from the nonferroelectric to the ferroelectric state, in contrast to known Pb-containing antiferroelectrics. Hence, the volume change and, in turn, the phase transition can be affected using uniaxial compressive stresses, and the effect on ferroelectricity can thus be assessed. It is found that the 0.94͑Bi 1/2 Na 1/2 ͒TiO 3 -0.05BaTiO 3 -0.01͑K 0.5 Na 0.5 ͒NbO 3 ceramic ͑largely ferroelectric͒, with a rhombohedral R3c symmetry, displays large ferroelectric domains, significant ferroelastic deformation, and large remanent electrical polarizations even at a 250 MPa compressive stress. In comparison, the 0.91͑Bi 1/2 Na 1/2 ͒TiO 3 -0.07BaTiO 3 -0.02͑K 0.5 Na 0.5 ͒NbO 3 ceramic ͑largely nonferroelectric͒ possesses characteristics of a relaxor ferroelectric ceramic, including a pseudocubic structure, limited ferroelastic deformation, and low remanent polarization. The results are discussed with respect of the proposed antiferroelectric nature of the nonferroelectric state.

High temperature stress-induced “double loop-like” phase transitions in Bi-based perovskites

“…11 Such studies are vital for their implementation into devices. The following study presents macroscopic ferroelastic hysteresis curves for polycrystalline BNT-6BT at various temperatures from 25 to 300°C.…”

Can an Electric Field Induce an Antiferroelectric Phase Out of a Ferroelectric Phase?

“…The strategy takes advantage of the fact that a poled FE ceramic contracts in volume when electric fields with a reversed polarity are applied and reaches a minimum volume around the coercive field ÀE c [12,18]. Since the compressive stress-induced FE-to-AFE phase transition is triggered by a critical volume contraction in FE oxides [16,17], it is conceived that the electric field-induced FE-to-AFE phase transition may also be realized and mediated by the volume contraction at ÀE c if the composition of the ceramic is properly tuned.…”

Mechanical confinement for improved energy storage density in BNT-BT-KNN lead-free ceramic capacitors

“…27,28,36 Tan et al reported that addition of KNN in increasing quantities was also responsible for reduced depolarization temperature and increasing non-ferroelectric characteristics of the original BNT-BT composition. 44 It was observed that 0.91(Bi 0.5 Na 0.5 )TiO 3 -0.07BaTiO 3 -0.02(K 0.5 Na 0.5 )NbO 3 possess largely pseudo-cubic structure in contrast to 0.94(Bi 0.5 Na 0.5 )TiO 3 -0.05BaTiO 3 -0.01(K 0.5 Na 0.5 )NbO 3 which was characterized by a rhombohedral R3c symmetry and displays largely ferroelectric behavior. 44 The significant change was observed for only 1 mol.% change in the amount of KNN.…”

“…44 It was observed that 0.91(Bi 0.5 Na 0.5 )TiO 3 -0.07BaTiO 3 -0.02(K 0.5 Na 0.5 )NbO 3 possess largely pseudo-cubic structure in contrast to 0.94(Bi 0.5 Na 0.5 )TiO 3 -0.05BaTiO 3 -0.01(K 0.5 Na 0.5 )NbO 3 which was characterized by a rhombohedral R3c symmetry and displays largely ferroelectric behavior. 44 The significant change was observed for only 1 mol.% change in the amount of KNN. For the purpose of our study we have used 0.91(Bi 0.5 Na 0.5 )TiO 3 -0.07BaTiO 3 -0.02(K 0.5 Na 0.5 )NbO 3 (BNT-BT-KNN) composition as it displays largely non-ferroelectric characteristics accompanied by large recoverable strains.…”