Piezoelectric and ferroelectric properties of (Bi_0.94−xLa_xNa_0.94)_0.5Ba_0.06TiO₃lead-free ceramics

Abstract

Lead-free piezoelectric ceramics (Bi0.94−x LaxNa0.94)0.5Ba0.06TiO3 have been fabricated by an ordinary sintering technique, and their piezoelectric and ferroelectric properties have been studied. The results of x-ray diffraction reveal that La3+ and Ba2+ diffuse into the Bi0.5Na0.5TiO3 lattices to form a new solid solution with a pure perovskite structure. After the partial substitution of La3+ for Bi3+ in the (Bi0.94−x Lax Na0.94)0.5Ba0.06TiO3 ceramics (x = 0–0.04), the ceramics exhibit a lower coercive field Ec and a larger remanent polarization Pr. Because of the large Pr and low Ec, the ceramics with x = 0.02–0.04 exhibit optimum piezoelectric properties: d33 = 181–196 pC N−1 and kP = 33.2–36.3%. The depolarization temperature Td decreases with increasing x (x = 0 − 0.04). At the high La3+ level (x = 0.06–0.12), the ceramics exhibit weak ferroelectricity and thus possess very poor piezoelectricity, and the low dielectric anomaly at Td disappears. In addition, the ceramics exhibit a relaxor characteristic, which probably results from the cation disordering in the 12-fold coordination sites. The temperature dependences of the ferroelectric and dielectric properties suggest that the ceramics with x = 0–0.04 may contain both polar and non-polar regions at temperatures above Td, while for the ceramics with x = 0.06–12, the polar and non-polar regions coexist at room temperature.

Preparation and electrical properties of Bi0.5Na0.5TiO3–BaTiO3–KNbO3 lead-free piezoelectric ceramics

“…The less saturated hysteresis loops and the weaker ferroelectricity of the BNBT-xKN ceramics with x > 0.04 may be attributed to two reasons: (i) possible occurrence of non-polar regions induced by the substitution of K 1+ for A site and Nb 5+ for B site in ABO 3 perovskite ferroelectrics in BNBT-xKN ceramics at room temperature. A similar result has been reported in (Bi 0.5 Na 0.5 ) 0.94 Ba 0.06 Zr y Ti 1−y O 3 and (Bi 0.94−x La x Na 0.94 ) 0.5 Ba 0.06 TiO 3 ceramics, in which the additive leads to the existence of non-polar regions [20,21]; (ii) high lever of additive will generate many defects due to charge compensation, and the defects will move at high electric field, which leads to the difficulty of saturated polarization at high field due to the leakage. Moderate content of additive KN enhances the phase transition between rhombohedra and tetragonal phase in MPB, which induces a high piezoelectric effect.…”

Effect of potassium concentration on the structure and electrical properties of lead-free Bi0.5 (Na,K)0.5 TiO3–BiAlO3 piezoelectric ceramics

“…5. Zheng et al [32] observed similar behavior in (Bi 0.94−x La x Na 0.94 ) 0.5 Ba 0.06 TiO 3 ceramics, in which T d decreased due to the substitution of La 3+ for Bi 3+ because of the existence of non-polar regions. Fig.…”

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

“…[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. 13 Compositional modifications with iso-and aliovalent dopants are technologically relevant because small doping amounts can modify considerably electrical properties due to cation vacancy formation and chemical pressure.…”

“…Specifically, La was widely used in several archetypal perovskite materials such as Pb(Zr,Ti)O 3 , and Ba 1/2 Na 1/2 TiO 3 . [16][17][18] Isovalent La-doping was shown to be a viable approach to tailor the dielectric and electromechanical properties of the BNT-BKT system. 13,16 Nevertheless, aliovalent doping was not yet used as a strategy, neither selective doping.…”