Investigation of Ga doping for non-stoichiometric sodium bismuth titanate ceramics

Abstract

The electrical performance of Ga 3+ doping Na0.5Bi0.5TiO3-based oxygen ion conductor was studied. The Na0.52Bi0.47Ti1-xGaxO3-δ (x=0, 0.01, 0.015, 0.02) samples were fabricated by the means of traditional solid-state reaction. The results of AC impedance measurement show that the bulk conductivity of Na0.52Bi0.47Ti1-xGaxO3-δ samples decrease monotonously with the increase of Ga 3+ doping. At 673 K, the bulk conductivity of the Na0.52Bi0.47Ti0.98Ga0.02O3-δ sample is 7.19×10 -4 S/cm, which is lower than that of Na0.52Bi0.47TiO3-δ sample under the identical test temperature. The highest total conductivity emerges in the Na0.52Bi0.47Ti0.99Ga0.01O3-δ sample with 1.387×10 -4 S/cm at 623 K for the Ga 3+ doping content of 1 mol%, which demonstrate that a slight of Ga 3+ doping supports the enhancement of the total conductivity. A relaxation peak was observed in the Na0.52Bi0.47Ti1-xGaxO3-δ compounds. As the Ga 3+ ions were introduced into the Na0.52Bi0.47TiO3-δ compound, there is an increasing trend of the relaxation activation energy educed by the internal friction test. In addition, the oxygen relaxtion height of Na0.52Bi0.47Ti1-xGaxO3-δ samples decreases along with the introduction of the Ga 3+ doping, suggesting that the introduction of the Ga 3+ leads to the decrease of mobile oxygen vacancy .

Electrical and Dielectric Properties of Ca-Doped Bi-Deficient Sodium Bismuth Titanate Na0.5Bi0.49−xCaxTiO3−δ (0 ≤ x ≤ 0.08)

“…Bhattacharyya et al [12] incorporated Mg 2+ to highly nonstoichiometric Na 0.54 Bi 0.46 TiO 3-δ and obtained the highest σ b by 1% Mg doping. The phenomenon that there exists an optimum doping level, above which σ b decreases with increasing doping level, has been widely observed in NBT with other B-site dopants such as Ga 3+ , Al 3+ , Sc 3+ , and Fe 3+ [8][9][10]15,16]. The limited enhancement of σ b by B-site acceptor doping was first explained by He and Mo by first-principles calculations [22].…”

“…In 2014, a new family of oxide ion conductors based on the ferroelectric perovskite sodium bismuth titanate (Na 0.5 Bi 0.5 TiO 3 , NBT) was reported [1]. Since then, numerous efforts have been devoted to enhancing the bulk conductivity (σ b ) of NBT by introducing A-site cation nonstoichiometry and/or acceptor doping [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21], based on which the following cognitions have been established: (1) high oxideion conductivity can be obtained in Na-rich or Bi-deficient NBT, e.g., Na 0.51 Bi 0.5 TiO 3.005 (N 0.51 BT) or Na 0.5 Bi 0.49 TiO 2.985 (NB 0.49 T) [2]; (2) acceptor doping, either on A-site (e.g., partial replacement of Bi 3+ by Sr 2+ [3]) or B-site (e.g., partial substitution of Ti 4+ by Mg 2+ [1]), generates oxygen vacancies by an ionic compensation mechanism, and therefore is an effective approach for enhancing the σ b of NBT [8]; (3) σ b of acceptor-doped NB 0.49 T is higher than that of yttria-stabilized zirconia (YSZ) at < 600 • C, and it shows no appreciable degradation at 500 • C contrary to the rapid conductivity decay for rare-earth-stabilized δ -Bi 2 O 3 [6], which makes NBT-based oxide ion conductors promising candidate electrolyte materials for IT-SOFCs.…”

Elucidating the capacitive behavior of Gd-doped BNT-BKT-BT electrodes in All-in-One supercapacitor devices

“…Recent research on understanding the role of structural defects in the form of oxygen vacancies in the electrode material has shown substantial improvement in the electrochemical performance of supercapacitors [18]. Researchers found that point defects, particularly oxygen vacancies, led to increased capacitance and decreased impedance of the electrode material in perovskite ceramics [19][20][21]. Interestingly, it was also experimentally reported that point defects in graphene oxide-based electrodes, such as oxygen-containing functional groups and vacancies, led to the same effect on the capacitance and impedance of the electrode material [22][23][24].…”