Grain and Grain Boundary Conductivities in Nanocrystalline Yttria-Stabilized-Zirconia Thin Films (original) (raw)
Related papers
Ionic conductivity of nanocrystalline yttria-stabilized zirconia: Grain boundary and size effects
Physical Review B, 2010
We report on the effect of grain size on the ionic conductivity of yttria-stabilized zirconia samples synthesized by ball milling. Complex impedance measurements, as a function of temperature and frequency are performed on 10 mol % yttria-stabilized zirconia nanocrystalline samples with grain sizes ranging from 900 to 17 nm. Bulk ionic conductivity decreases dramatically for grain sizes below 100 nm, although its activation energy is essentially independent of grain size. The results are interpreted in terms of a space-charge layer resulting from segregation of mobile oxygen vacancies to the grain-boundary core. The thickness of this space-charge layer formed at the grain boundaries is on the order of 1 nm for large micron-sized grains but extends up to 7 nm when decreasing the grain size down to 17 nm. This gives rise to oxygen vacancies depletion over a large volume fraction of the grain and consequently to a significant decrease in oxide-ion conductivity.
Grain Boundary Blocking Effect in Yttria Stabilized Zirconia Thin Films
ECS Transactions, 2012
The cross-plane oxygen ion conductivity of yttria stabilized zirconia thin films prepared by aerosol assisted chemical vapor deposition is strongly influenced by the thin film microstructure. Thin films with highly textured columnar grains oriented parallel to the current direction exhibit significantly higher conductivity than thin films with randomly oriented nanocrystalline microstructure, where ionic transport proceeds through the numerous grain boundaries. The total conductivity of columnar AA-CVD thin films is consistent with literature values on oxygen ion conduction through chemically pure YSZ grains as determined for microcrystalline samples, while that of the nanocrystalline specimens is similar to corresponding specific grain boundary conductivities.
Solid State Ionics, 2002
The influence of alumina additions on grain boundary electrical conductivity of yttria-doped zirconia has been investigated by impedance spectroscopy. The results have been interpreted taking into account the microstructural and microchemical characterizations. Experiments have been conducted on polycrystals sintered from powders prepared through two different processing routes. Samples with the cleaner microstructure and no evidence for grain boundary glassy films show the highest conductivities, which decrease in the presence of alumina additions. On the contrary, alumina additions ( V 2 mol%) lead to an increase of conductivity of samples showing grain boundary glassy films. These results have been attributed to a change in the glassy phase wettability due to the higher amount of Al found in the glassy phases in the presence of alumina additions. The same grain boundary activation energy found for the different samples suggests that only ''clean'' grain boundaries contribute to the transport processes. D
The separation of grain and grain boundary impedance in thin yttria stabilized zirconia (YSZ) layers
Solid State Ionics, 2011
An improved electrode geometry is proposed to study thin ion conducting films by impedance spectroscopy. It is shown that long, thin, and closely spaced electrodes arranged interdigitally allow a separation of grain and grain boundary effects also in very thin films. This separation is shown to be successful for yttria stabilized zirconia (YSZ) layers thinner than 20 nm. In a series of experiments it is demonstrated that the extracted parameters correspond to the YSZ grain boundary and grain bulk resistances or to grain boundary and substrate capacitances. Results also show that our YSZ films produced by pulsed-laser deposition (PLD) on sapphire substrates exhibit a bulk conductivity which is very close to that of macroscopic YSZ samples.
physica status solidi (a), 2012
The electrical cross-plane conductivity of 8 mol% yttria stabilized zirconia (YSZ) thin films prepared by different deposition techniques, namely aerosol assisted chemical vapor deposition, wet spray pyrolysis (SP), and pulsed laser deposition (PLD), is correlated with their microstructure. Depending on deposition technique and process conditions, microstructures ranging from amorphous to randomly oriented nanocrystalline or columnar with preferred (111) orientation are obtained. Cross-plane AC impedance measurements of these thin films show that the oxygen ion conductivity of randomly oriented nanocrystalline samples is determined by the grain boundaries, which show significantly lower transport properties than the grain interior. In columnar microstructures, the conductivity is determined by ionic transport through the grains only. The same conduction behavior is found for amorphous and randomly oriented microstructures with grain sizes between 3 nm and 9 nm, indicating that no true size effects occur in 8 mol% YSZ.
Yttria-zirconia: Effect of microstructure on conductivity
Journal of Materials Science, 1987
Complex impedance measurements and detailed analysis of the grain-boundary microstructure have been made on fully stabilized yttria-zirconia sintered bodies as a function of grain size. The prereacted yttria-zirconia powder used in this study was obtained from a commercial source. The powder has very high reactivity and starts sintering around 1 200 ° C. The densification process is complete around 1 350°C but the grain growth continues almost linearly with sintering temperature. The grain size variation obtained was between 1 and 30#m. The grainboundary resistivity when plotted against grain size showed an inflection in the vicinity of 1 500°C sintering temperature. These results have been explained in terms of the grainboundary microstructure changing with the sintering temperature. The thickness of the grainboundary layer determined from impedance data and transmission electron micrographs are in reasonably good agreement. The activation energy for the grain-boundary resistivity was only slightly higher than that for the lattice resistivity.
Effect of ion implantation doping on electrical properties of yttria-stabilized zirconia thin films
Solid State Ionics, 1992
The change in conductivity of Fe and Ti implanted if-sputtered layers of yttria-stabilized zirconia (YSZ) was studied as a function of the temperature (400-800 °C) and oxygen partial pressure. In an oxidized state and in the temperature range of 400-600 ° C, the conductivity of the Fe implanted YSZ film ( 15 keV, 8 × 10 '6 at.cm -2) was dominated by the n-type electronic conductivity of a thin Fe203 layer with an estimated thickness of less than 2 nm on top of the YSZ thin film. Due to the incorporation of a part of the implanted Fe atoms in the yttria-stabilized zirconia lattice, the ionic conductivity was somewhat decreased. In a reducing atmosphere this electronic conduction was no longer observed. In an oxidized state, the conductivity of the YSZ film was not influenced by the implantation of Ti ( 15 keV, 8 X 1016 at.cm-2). After reduction in a H2 atmosphere, an increase in the conductivity of the sputtered film with 2-3 orders of magnitude was observed. This has been ascribed to the presence of nonstoichiometric TiO2_x, which is an n-type semiconductor.