Synthesis and electrical characterisation of doped perovskite titanates as potential anode materials for solid oxide fuel cells

Abstract

This work reports the synthesis and electrical characterisation over a range of oxygen partial pressures (10^–20–1 atm) of the A-site deficient perovskites Sr_1–3x/2La_xTiO_3–δ, with a view to establishing their potential as anode materials for solid oxide fuel cells. Single phase samples were observed for synthesis in air for 0≤x≤0.6, and the materials remained phase pure for both high and low oxygen partial pressures at the measurement temperature of 930 °C. Good electrical conductivity, which increased with increasing La content, was observed on reduction in low oxygen partial pressures, with values as high as 7 S cm^–1 [ P(O₂)= 10^–20 atm], similar to values observed for the related system, Sr_1–x/2Ti_1–xNb_xO_3–δ, examined previously. The conductivity of the fully reduced samples showed metallic character from 100 to 930 °C. As the oxygen partial pressure was raised, the conductivity dropped, showing an approximate [P(O₂)]^–1/6 dependence for porous samples. New samples, Sr_{1–y/2–3x/2}La_xTi_1–yNb_yO_3–δ, with both La and Nb substitutions, were also studied, and these phases showed similar electrical behaviour. Further results for the Sr_1–x/2Ti_1–xNb_xO_3–δsystem are presented and compared with the La doped systems.