The niobates with large cations of barium and strontium have been identified as potential solid oxide fuel cell materials for the first time. Both SrNb2O6 and BaNb2O6 have several types of crystal structures, and according to density functional theory (DFT) calculations the most stable structures were found to be P21/c for SrNb2O6 and C2221 for BaNb2O6. These structures were then used to calculate conductivity characteristics. Crystal chemical approaches confirmed that 2D oxygen diffusion is plausible in SrNb2O6, with a migration energy below 0.4 eV, and 3D diffusion is possible in BaNb2O6, with a lower migration energy than 0.7 eV. Kinetic Monte Carlo simulations revealed that the O2−-ionic conductivity of SrNb2O6 was an order of magnitude higher than that of BaNb2O6 across the entire temperature range. Both compounds were synthesized using the Pechini method and resulting samples had the same space groups as predicted by quantum-chemical calculations. The samples exhibited high stability over a wide range of oxygen pressure, and in a CO2 atmosphere. The measurements of total conductivity showed values of 3.2 × 10− 5 Ω−1 × cm− 1 in SrNb2O6 and 1.8 × 10− 5 Ω−1 × cm− 1 at 900 °C in BaNb2O6, respectively. The conductivity measurements in a humid environment confirmed the presence of proton diffusion in BaNb2O6. The conductivity as a function of oxygen partial pressure confirmed the existence of n-type conductivity in BaNb2O6, while SrNb2O6 exhibited predominantly ionic conductivity. Therefore, ionic transport numbers were also measured using the electromotive force method. SrNb2O6 had transport numbers exceeding 90% across the entire temperature range, whereas BaNb2O6 showed similar values up to 600 °C. After the decrease in oxygen transport was observed in BaNb2O6, confirming the presence of n-type conductivity. Despite the low conductivity values, these materials have shown high chemical and thermal stability, and they can serve as the initial matrix for developing methods to improve conductivity. Graphical abstract

The stability and conductive properties of the MNb₂O₆ phases (M = Ba, Sr): full theoretical and experimental study

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发表日期：

2025年9月19日

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Yelizaveta A. Morkhova,
Anastasia V. Egorova,
Mariia S. Koroleva,
Elizaveta D. Merzlyakova,
Valeria S. Legonkova,
Artem A. Kabanov

摘要

The niobates with large cations of barium and strontium have been identified as potential solid oxide fuel cell materials for the first time. Both SrNb₂O₆ and BaNb₂O₆ have several types of crystal structures, and according to density functional theory (DFT) calculations the most stable structures were found to be P2₁/c for SrNb₂O₆ and C222₁ for BaNb₂O₆. These structures were then used to calculate conductivity characteristics. Crystal chemical approaches confirmed that 2D oxygen diffusion is plausible in SrNb₂O₆, with a migration energy below 0.4 eV, and 3D diffusion is possible in BaNb₂O₆, with a lower migration energy than 0.7 eV. Kinetic Monte Carlo simulations revealed that the O²⁻-ionic conductivity of SrNb₂O₆ was an order of magnitude higher than that of BaNb₂O₆ across the entire temperature range. Both compounds were synthesized using the Pechini method and resulting samples had the same space groups as predicted by quantum-chemical calculations. The samples exhibited high stability over a wide range of oxygen pressure, and in a CO₂ atmosphere. The measurements of total conductivity showed values of 3.2 × 10^− 5 Ω⁻¹ × cm^− 1 in SrNb₂O₆ and 1.8 × 10^− 5 Ω⁻¹ × cm^− 1 at 900 °C in BaNb₂O₆, respectively. The conductivity measurements in a humid environment confirmed the presence of proton diffusion in BaNb₂O₆. The conductivity as a function of oxygen partial pressure confirmed the existence of n-type conductivity in BaNb₂O₆, while SrNb₂O₆ exhibited predominantly ionic conductivity. Therefore, ionic transport numbers were also measured using the electromotive force method. SrNb₂O₆ had transport numbers exceeding 90% across the entire temperature range, whereas BaNb₂O₆ showed similar values up to 600 °C. After the decrease in oxygen transport was observed in BaNb₂O₆, confirming the presence of n-type conductivity. Despite the low conductivity values, these materials have shown high chemical and thermal stability, and they can serve as the initial matrix for developing methods to improve conductivity.

Graphical abstract

The stability and conductive properties of the MNb2O6 phases (M = Ba, Sr): full theoretical and experimental study

摘要

The stability and conductive properties of the MNb₂O₆ phases (M = Ba, Sr): full theoretical and experimental study