Abstract
The influence of Mg-doping on the phase formation and conductivity of Na-excess Na0.5Bi0.5TiO3 (NBT) has been studied for its possible electrolyte applications in SOFCs. Dense ceramic bulk specimens are fabricated using the conventional solid oxide reaction route with the sintering temperature of 1000 °C. Phase analysis reveals the existence of a minor secondary phase along with the dominant perovskite phase. The secondary phases are identified to be based on sodium titanate in Na0.54Bi0.46TiO3-δ, and Na0.9Ti1.55Mg0.45O4 in Mg-doped compositions. A substantial enhancement in the grain conductivity is seen by substituting 1 mol% Mg2+ for Ti present at the B-site of NBT. At 600 °C, the grain conductivity is observed to be 14.3 mS cm−1 which is ∼68% higher than the best reported NBT based composition. However, adding more than 1 mol% Mg2+ leads to a decrease in the grain conductivity. A correlation between the conductivity and phase formation has been proposed which can explain the conductivity behaviour on Mg addition in Na-excess NBT.
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