Influence of A-Site Deficiency and Ca Concentration on the Electrical and Crystallographic Properties of (NdSr Ca ) TiFeO-Based Fuel Electrode for Solid Oxide Cells.

This study explores the impact of A-site deficiency and Sr/Ca ratio on the electrochemical and crystallographic properties of a (NdSr Ca ) TiFeO hydrogen electrode for solid oxide cells under reducing and air atmospheres. 5% and 10% A-site deficient (NdSr Ca ) TiFeO ( = 0.35-0.45, = 1.05, 1) (referred to as 5NSCTF- and 10NSCTF-) materials were studied, while the ratio between A-site cations was kept the same with both deficiencies. The results demonstrate that the extent of A-site deficiency and the Ca concentration in the A-site have a significant impact on the microstructure (sinterability), conductivity, and catalytic activity of electrodes. Segregation of Nd from the lattice with 5% A-site deficiency was observed as a result of thermal treatment at low pO. Among the studied materials, the highest total electrical conductivity of porous electrode layer at 850 °C and in 97% H + 3% HO atmosphere was 4.8 S cm observed for the NdSrCaTiFeO (10NSCTF-35). The highest electrochemical performance was observed in the case of NdSrCaTiFeO (10NSCTF-45), which showed a polarization resistance value equal to 0.19 Ω cm after 100 h of stabilization at 800 °C in a humidified (1.7% HO) H atmosphere. The best electrochemical performance with 606 mW cm power density at 850 °C in 98.3% H + 1.7% HO atmosphere was demonstrated by a 50 wt % NdSrCaTiFeO + 50 wt % CeGdO composite.