Effects of Cr/Ti co-doping on the electrical and thermal properties of tantalum-based electrolyte materials for solid ox
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Effects of Cr/Ti co-doping on the electrical and thermal properties of tantalum-based electrolyte materials for solid oxide fuel cells Shuang Ding1, Junwei Zhang1, Shun Yang1, Ziyang Song1, Hong Jiang1, Changjiu Li1,* Yongjun Chen1 1
, and
State Key Laboratory of Marine Resource Utilization in South China Sea (Hainan University) and Special Glass Key Lab of Hainan Province, Hainan University, Haikou 570228, China
Received: 20 February 2020
ABSTRACT
Accepted: 17 August 2020
New triclinic oxide material Ta1-x-yTixCryO2.5-d (x = 0.077, y = 0–0.053) was synthesized via an oxalate co-precipitation method and tested as a novel electrolyte for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Structural, electrical, and thermal properties of tantalum-based electrolyte co-doping with Cr3?/Ti4? content were studied. X-ray powder diffraction showed that the crystal structure changed from orthorhombic to triclinic due to co-doped, and its high-temperature triclinic (pseudo-tetragonal) phase of tantalum pentoxide (HTa2O5) structure was stabilized to room temperature by doping. The crystalline phase facilitates the generation of more oxygen vacancies, which increases the electrical conductivity. The appearance of oxygen vacancies in the crystal with triclinic structure was confirmed with Raman spectroscopy and X-ray photoelectron spectroscopy. Scanning electron microscopy results exhibited the grain size decreases gradually with doping. Impedance curves showed high total ionic conductivity (1.48 9 10–1 S/cm at 700 C) and low activation energy (Ea = 0.857 eV) for Ta0.9Ti0.067Cr0.033O2.5-d. Thermal expansion coefficients (3.09 9 10–6 K-1) for co-doped samples were much lower in comparison to other electrolytes. Based on the results reported in this work, Ta1-x-yTixCry O2.5-d can be an excellent oxygen conductor and recommended as solid electrolytes for IT-SOFC applications.
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1 Introduction Solid oxide fuel cell (SOFC) directly converts chemical energy into electric power by oxidizing fuel at intermediate temperatures [1, 2]. Compared with
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https://doi.org/10.1007/s10854-020-04286-7
other more conventional methods, SOFC-based environmental processes are advantageous because of their use of high energy and their method of producing electricity. Thus, research using SOFC-based technologies to solve the energy crisis has attracted a
J Mater Sci: Mater Electron
lot of attention [3–5]. Electrolyte is a major component of SOFCs. However, active materials must be carefully and thoughtfully selected to obtain highperformance electrolyte. SOFC electrolytes based on yttria-stabilized zirconia (YSZ) are very popular because of their high oxygen-ion conductivity (about 0.016 S/cm at 1023 K) and phase stability [6]. To lower the operating temperature and improve ionic conductivity of SOFC electrolytes that are based on YSZ, much research has been done regarding doping techniques and the synth
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