Anisotropic oxide ion conduction in melilite intermediate temperature electrolytes

• Main Authors: Wei, Fengxia, Gasparyan, Hripsime, Keenan, Philip J., Gutmann, Matthias, Fang, Yanan, Baikie, Tom, Claridge, John B., Slater, Peter R., Kloc, Christian Leo, White, Timothy John
• Other Authors: School of Materials Science & Engineering
• Format: Article
• Language: English
• Published: 2016
• Subjects: Structure-property relation; Anisotropic oxide ion conduction; Electrolyte
• Online Access: https://hdl.handle.net/10356/81856; http://hdl.handle.net/10220/39743
• Institution: Nanyang Technological University

Electrolytes with oxide ion conductivities higher than 10−2 S cm−1 at moderate temperatures (∼500–900 °C) offer the possibility for solid oxide fuel cells to operate with less maintenance. This study of [A1+xB1−x]2[Ga]2[Ga2O7+x/2]2 (0 ≤ x ≤ 0.5) (A = La, Nd; B = Ca, Sr) layered-melilite found that in large single crystals intralayer oxide ion conduction is dominant. This anisotropic behavior arises by relaxation about the interstitial oxygen through changes in the interlayer A and Ga coordination, and at 850 °C conductivities are ∼0.008 S cm−1 along the c direction and ∼0.036 S cm−1 perpendicular to the c axis. It is found that the ionic conductivity can be optimized by increasing the number of interstitial oxygen and reducing the size of interlayer cations.