Electronic conductivity enhancement of (La,Sr)TiO3 with Nb-doping on B-Site
B-site doped, A-site deficient strontium titanates with general formula LaxSr1-3x/2+γxNbyTi1-yO3-δ (x = 0.2, 0.25, 0.3, 0.35, 0.4; y = 0, 0.02, 0.03; γ = 0.03) were produced by flame spray synthesis and the electrical conductivity of dense ceramic bars sintered under reducing conditions measured over broad temperature and oxygen concentration ranges. As-synthesized powders were nano-scale and slightly reduced, while it was observed that sinterability was promoted by both La substitution and Nb doping. Electrical conductivity measurements on dense bars under reducing conditions revealed that stoichiometric substitution of Ti4+ by Nb5+ raised conductivity by approx. 40%, with a maximum value of 226 S cm−1 observed at 900 °C. This was attributed to a higher concentration of Ti'Ti defects, due to concurrent and enhanced oxygen vacancy (VO) formation under reducing conditions. The electronic properties of a slightly porous bar sample of the La0.3Sr0.559Nb0.02Ti0.98O3-δ composition were found to be stable over one redox cycle.
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