High Curie temperature BiFeO3-BaTiO3 lead-free piezoelectric ceramics: Ga3+ doping and enhanced insulation properties

Abstract

BiFeO3-BaTiO3 is a promising high-temperature lead-free piezo-ceramics due to its high Curie temperature (TC > 500 °C) and excellent piezoelectric properties. However, a high leakage current was often detected in this system, which severely affects its applications. In this work, the 0.7BiFe(1−x)GaxO3-0.3BaTiO3 (BFGax-BT, 0.00 ≤ x ≤ 0.10) system was designed to reveal the reason of leakage-current density decreased by their leakage mechanism. Because of the suppression of generation of Fe2+ and oxygen vacancy (VO∙∙), the leakage mechanism from space charge limited conduction mechanism found in Ga-free BF-BT ceramics turns into Ohmic conduction and Schottky emission mechanism as Fe3+ was replaced with Ga3+. A good combination of piezoelectric properties (d33 = 174 pC N−1 and kp = 29%) and high Curie temperature (TC = 497 °C) was achieved in the BFGa0.06-BT ceramic owning the lowest leakage-current density. This work will provide the clues for preparing the high insulation and high piezoelectric performance BF-BT-based ceramics by suppressing the valence change of Fe3+ and VO∙∙ appearance.

Establishing a Relationship between the Piezoelectric Response and Oxygen Vacancies in Lead-Free Piezoelectrics

“…Enhanced electric properties with d 33 = 165 pC/N, T C = 505 °C, J = 10 –9 A/cm 2 , and k p = 26% are achieved . A good combination of piezoelectric properties ( d 33 = 174 pC N –1 and k p = 29%) and a high T C of 497 °C is achieved in Ga 3+ -doped BF–BT ceramics by suppressing the valence change of Fe 3+ and generation of oxygen vacancies and making ρ increase . It seems that the existence of oxygen vacancies is not beneficial for piezoelectricity improvement.…”

“…18 A good combination of piezoelectric properties (d 33 = 174 pC N −1 and k p = 29%) and a high T C of 497 °C is achieved in Ga 3+ -doped BF−BT ceramics by suppressing the valence change of Fe 3+ and generation of oxygen vacancies and making ρ increase. 19 It seems that the existence of oxygen vacancies is not beneficial for piezoelectricity improvement. However, an opposite phenomenon has also been reported in other material systems.…”

Relaxation degree and defect dipoles‐controlled resistivity and leakage current in BF–BT‐based ceramics

“…Recently, the leakage mechanism in Bi‐based ceramics can be effectively controlled by different heat treatment methods 10 . Moreover, for Ga‐doped BF–BT ceramics, the leakage current mechanism from the space‐charge‐limited conduction mechanism turns into Ohmic conduction and the Schottky emission mechanism as Fe 3+ was replaced with Ga 3+ 11 . However, the leakage current mechanism for BF–BT‐based ceramics has not yet been agreed upon, and the study of the leakage current behavior is relatively lacking.…”

“…10 Moreover, for Ga-doped BF-BT ceramics, the leakage current mechanism from the space-charge-limited conduction mechanism turns into Ohmic conduction and the Schottky emission mechanism as Fe 3+ was replaced with Ga 3+ . 11 However, the leakage current mechanism for BF-BT-based ceramics has not yet been agreed upon, and the study of the leakage current behavior is relatively lacking. In addition, regulating the degree of relaxation of BF-based ceramics to achieve a breakthrough in performance is also an important entry point.…”

Boosting the High Performance of BiFeO3-BaTiO3 Lead-Free Piezoelectric Ceramics: One-Step Preparation and Reaction Mechanisms

“…BiFeO 3 has gained increasing attention due to its coexisting ferroelectric and antiferromagnetic properties. − It is a rhombohedral (R) perovskite with a high Curie temperature ( T C of ∼830 °C) and displays antiferromagnetism below 370 °C. − BiFeO 3 is polarized due to the Bi 3+ lone electron pair, and its magnetization originates from the presence of Fe 3+ . − A high spontaneous polarization (∼100 μC/cm 2 ) was measured in BiFeO 3 thin films, , which gives the material a wide application potential in multifunctional devices. Other than extensively studied thin films, the improvement of BiFeO 3 ceramics is difficult due to the existence of Bi 25 FeO 39 and Bi 2 Fe 4 O 9 .…”