X-ray diffraction and electron parametric resonance investigations on the fluorite material Y0.25Ti0.15Zr0.6O2-x

The compound Y0.25Ti0.15Zr0.6O2-x, to be used as an anode material in solid oxide fuel cells, was synthesized by coprecipitation. X-ray diffraction after sintering at different temperatures revealed no single-phase material up to 1500 degreesC but indicated two fluorites with different lattice parameters. The inhomogeneity of the material arose from a cation demixing process around 1100-1200 degreesC, leading to an intermediate fraction of a pyrochlore phase. After reduction in Ar/4% H-2 at 1000 degreesC, a small decrease (about 0.1%) in the lattice parameter was observed. The electron paramagnetic resonance measurements on reduced samples showed the occurrence of Ti3+ ions in at least two sites. Possible reasons for the decrease of the lattice parameter after reduction are discussed