NbTi 0.5Ni 0.5O 4 as anode compound material for SOFCs

NbTi _0.5Ni _0.5O ₄ (NTNO) has been prepared using solid state synthesis and investigated as a potential anode material. The oxide form of NTNO has single phase rutile-type structure with tetragonal (P42/mnm) space group. The reduced form is a composite of nano-scaled particles of metallic Ni and Nb _1.33Ti _0.67O ₄ phase. Reduced NTNO showed high electronic conductivity up to 280 S.cm ^{- 1} at 900 °C in reducing atmosphere, but suffers from low CTE equal to 3.78 10 ^{- 6} K ^{- 1}. Studies of NTNO as anode material were carried out in a three electrode - electrochemical half cell configuration under pure humidified H ₂ at 900 °C using a 2 mm thick zirconia electrolyte and without any additional current collector material. The results show a reasonable series resistance (R _s) equal to 2.7 Ωcm ² (about 50% higher than for metallic gold layers) indicating a good current collection performance for a 10 μm layer of material. The polarization resistance (R _p) was equal to 33 Ωcm ² and is attributed to a poor density of three phase boundaries (TPB) and shortage of oxide ion conduction in the anode layer. The results show the potential of NTNO as an anode material, especially after optimization of the microstructure towards the increase of TPB length.