| Yttria-stabilized zirconia with 5 to 10 mole % TiO{dollar}sb2{dollar} (YZT) is a likely candidate for solid oxide fuel cell (SOFC) anode material because it exhibits oxygen-ion and electronic conductivity at 800 to 1000 C, is very stable, and would be compatible with a stabilized zirconia electrolyte. The electronic conduction mechanism of YZT had been previously attributed to small polaron hopping between the 3+ and 4+ oxidation states of titanium. This mechanism is confirmed by correlating the increase of the electrical conductivity of the YZT under reduced oxygen pressures to its Ti{dollar}sp{lcub}3+{rcub}{dollar} content. The conductivity of YZT having 10 mole % TiO{dollar}sb2{dollar} shows an increase typical of n-type conduction at 570 and 840 C at oxygen pressures below 10{dollar}sp{lcub}-22{rcub}{dollar} and 10{dollar}sp{lcub}-15{rcub}{dollar} atm, respectively. An electron paramagnetic resonance study shows that the concentration of Ti{dollar}sp{lcub}+3{rcub}{dollar} in the YZT increases as its TiO{dollar}sb2{dollar} content increases from 1 to 15 mole %, the oxygen pressure decreases for 10{dollar}sp{lcub}-11{rcub}{dollar} to 10{dollar}sp{lcub}-17{rcub}{dollar} atm, and the temperature increases from at 620 to 860 C. Percolation theory is used to explain how small polarons hop in the YZT lattice when as few as 3.4 % of the cation sites are occupied by titanium.; Uniform thin films of YZT are prepared by metal-organic deposition (MOD). Zr-, Y- and Ti-ethylhexanoate solutions are spun onto platinum, yttria-stabilized zirconia, and sapphire substrates and heated to remove the organics and form a ceramic thin film. No residual carbon is observed in thin films that are heated on a hot plate at 530 C for five to ten minutes. Cracking is observed in films greater than 300 A thick; thicker films are made by stacking several 300 A films. Attempts to measure the conductivity of these films is unsuccessful. Measurements made in the direction perpendicular to the films are short-circuited by pin-holes in the films, and those made in parallel with the film are affected by the formation of resistive Zr-Rh phases caused by a reaction of the YZT films with the Pt/Pt-Rh electrodes. |
