Influence of sintering profile on the microstructure and electronic transport properties of Sr(Ti,Nb)O3 tapes for solid oxide cell applications

Nb-doped strontium titanate (Sr0.99Ti0.9Nb0.1O3, STN) tapes were fabricated by tape casting and used for investigating the influence of pre-treatment temperature on the sintering behavior, microstructure and electronic properties. The pre-treatment temperature was varied between 500 degrees C and 800 degrees C. Phase analysis of the powder from the pre-treatment step showed a single phase up to 700 degrees C and a Sr-enriched secondary phase beyond 700 degrees C. Sintering dilatometry showed similar sintering behaviour with little variation in the final shrinkage with different pre-treatment temperatures. Backscattered electron imaging confirmed the presence of Sr enriched secondary phase for pre-treatment at 700 degrees C or above. Conductance mapping on samples pre-treated at 800 degrees C and sintered at 1450 degrees C exhibited regions of low conductance. Conductivity measurements of pre-treated and sintered, at 1300 degrees C, samples showed decrease in conductivity with increasing pre-treatment temperature. These observations enhance the understanding of processing STN materials for solid oxide cells applications significantly.