Ionic conductivity studies of ultrafine-grained yttria stabilized zirconiapolymorphs

Ultrafine-grained zirconia ceramics doped with yttria in different concentr ations from 2 to 12 mol% were prepared by chemical precipitation method wit h an average grain size of 10 nm. The ac ionic conductivity studies reveale d that 3 mol% yttria stabilized zirconia (3YSZ) in tetragonal phase shows m aximum conductivity both in grains and grain boundaries for a range of temp eratures. In the coarser grained zirconia systems, with different yttria co ncentration, the conductivity maximum is usually observed in the cubic phas e field with 8 mol% Y2O3. The shift of the maximum conductivity with the yt tria content towards the lower concentration (3 mol%) is attributed to the grain size effect. The Arrhenius plot of the total de conductivity is found to follow that of the grain boundaries rather than the grains, showing tha t the total conductivity is mainly influenced by the grain boundaries in th e ultrafine-grained materials. (C) 1999 Elsevier Science B.V. All rights re served.