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

M Y Li,C He,X Y Li,X F Wang,W G Wang,G L Hao,D Wang,T Liu

doi:10.1007/s10854-021-06158-0

M Y Li, C He + Show 6 more

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https://doi.org/10.1007/s10854-021-06158-0

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Abstract

The electrical properties of Ga3+ doping Na0.5Bi0.5TiO3-based oxygen ionic conductors were 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 measurements showed that the bulk conductivity of Na0.52Bi0.47Ti1−xGaxO3−δ samples decreased monotonously with the increase of Ga3+ doping concentration. 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 the Na0.52Bi0.47TiO3−δ sample under the identical test temperature. The highest total conductivity emerged in the Na0.52Bi0.47Ti0.99Ga0.01O3−δ (x = 0.01) sample with 1.387 × 10–4 S/cm at 623 K, which demonstrated that the slight Ga3+ doping supported the enhancement of the total conductivity. A relaxation peak was observed in Na0.52Bi0.47Ti1−x GaxO3−δ compounds. As the Ga3+ ions were introduced into the Na0.52Bi0.47TiO3−δ compound, there was an increasing trend of the relaxation activation energy educed by the internal friction test. In addition, the oxygen relaxation height decreased with Ga3+ doping, which suggested that the introduction of Ga3+ ions resulted in the decrease of mobile oxygen vacancy.

Highlights

IntroductionTo get the higher electrical properties in the NBT based oxygen ion conductors, higher oxygen vacancy content is necessary
Oxygen ion conductors have been quite broadly used, such as oxygen pumps, oxygen separation membranes and solid oxide fuel cells (SOFC), etc.[1,2,3,4,5,6]
Yang et al Reported that Sr2+ doped Bi-deficent NBT-based compounds (Na0.5Bi0.47Sr0.02TiO2.975) is a profitable means to improve the electrical properties for oxygen ion conductors[14]

Summary

Introduction

To get the higher electrical properties in the NBT based oxygen ion conductors, higher oxygen vacancy content is necessary. Yang et al Reported that Sr2+ doped Bi-deficent NBT-based compounds (Na0.5Bi0.47Sr0.02TiO2.975) is a profitable means to improve the electrical properties for oxygen ion conductors[14]. Ga3+ (0.062 nm) is very close to that of Ti4 + (0.061 nm) leading to a small elastic strain energy which is beneficial to the formation of stable solid solution[1,2], Ga3+ ion was selected as a acceptor ion to substitute the B-site Ti4+ ions included the Bi-deficent Na0.52Bi0.47TiO3-δ compound to gain the higher electrical properties of NBT oxygen ion conductors. There were no extra peaks of impurity phase in the compositions of Na+ excess and Ga3+ doped NBT samples through comparing the diffraction pattern with Na0.5Bi0.5TiO3 compound , which suggested that excess Na+ and Ga3+ ions are dissolved into the perovskite lattice of NBT-based compounds[13]. The tolerance factor for the Na0.52Bi0.47Ti1-xGaxO3-δ (x=0, 0.01, 0.015, 0.02) samples was virtually unchanged, which indicates that Ga3+ doping has very little effects on the lattice distortion

Ionic conductivity Figure 2 represents the complex impedance spectra for the

Discussion

Conclusion