Niobium based tetragonal tungsten bronzes as potential anodes for solid oxide fuel cells: synthesis and electrical characterisation

In this paper we report studies on a range of niobate based tungsten bronzes, with a View to analysing their potential as anode materials in SOFCs. Six systems were studied, (Sr1-xBax)(0.6)Ti0.2Nb0.8O3, Sr0.6-xLaxTi0.2+xNb0.8-xO3, (Sr0.4-xBax)Na0.2NbO3, (Ba1-xCax)(0.6)Ti0.2Nb0.8O3, Ba(0.5-x)A(x)NbO(3) (A = Ca, Sr), and Ba0.3NbO2.8, and the electrical conductivities were examined over a range of oxygen partial pressures (10(-20)-1 bar). All the systems showed good conductivity in low oxygen partial pressures, with values as high as 8 S cm(-1) at 930 degrees C (P(O-2) = 10(-20) bar). As the oxygen partial pressure was raised the conductivity dropped showing in most cases an approximate [P(O-2)](-1/4) dependence and good re-oxidation kinetics. Of all the samples studied the (Sr1-xBax)(0.6)Ti0.2Nb0.8O3 and (Ba1-xCax)(0.6)Ti0.2Nb0.8O3 systems appear most promising for potential use as anode materials in SOFCs. (C) 1999 Elsevier Science B.V. All rights reserved.