STRUCTURAL AND ELECTRICAL CHARACTERIZATION OF TITANIA-DOPED YSZ

Solid solutions and composites based on YSZ yttria-stabilized zirconia ) with titania additions up to 20 mol% were prepared by solid state re action. Structural characterization included XRD and Raman spectroscop y. Electroded samples were also studied by impedance spectroscopy in a ir between 573 and 1273 K. The ionic conductivity of these solid solut ions decreases with increasing titania content. A sharp drop in conduc tivity is observed for specimens with compositions near to the usually assumed solubility limit of titania in the fluorite phase (about 10 m ol%). This decrease is of almost one order of magnitude with respect t o undoped or lightly doped samples. A smaller composition dependence i s observed for higher titania additions (10-20 mol% TiO2). Raman resul ts show that tetragonal short range order is found in the cubic fluori tic phase well below the 10 mol% TiO2 addition. This short range order is expained by the ability of Ti to achieve a sixfold oxygen coordina tion. As a consequence, a decrease in the concentration of mobile oxyg en vacancies is expected, which is the reason for the electrical condu ctivity decrease. (C) 1997 Elsevier Science Limited.