Blocking Effect in High Purity Nanostructured Cubic Zirconia Ceramics

Abstract

International audienceElectrical properties of grain boundaries, free of any secondary phases, have been investigated in cubic nanostructured zirconia ceramics. Pure 8YSZ powders were synthesised by spray pyrolysis process. These powders were used to perform dense nanostructured ceramics using two compaction techniques: cold isostatic pressing (CIP) and hot uniaxial pressing (HUP) in an oxidising atmosphere. Grain sizes ranging from 25 to 242 nm and relative densities from 93 up to 98% were obtained. Electrical contribution of the bulk and the blocking effect due to grain boundaries were determined by impedance spectroscopy and analysed according to the brick layer model. The additional blocking effect is a decreasing function of the grain size but its magnitude reaches a plateau quite insensitive to the grain size below 100 nm. This indicates that the recorded electrical contribution originates from an intrinsic effect. This can be related to a dominant electrical contribution of space charge layers located at the grain boundaries area of nanoscale grain sizes

Influence of microstructure on the cross‐plane oxygen ion conductivity of yttria stabilized zirconia thin films

“…Most studies on the ionic transport properties of polycrystalline yttria stabilized zirconia (YSZ) report that nanocrystalline samples exhibit significantly lower total conductivities than microcrystalline samples 1–9. The reduced transport properties of grain boundaries in highly pure YSZ have been related to the large number of displaced atoms, which entail an electrical distortion.…”

Synthesis and ion conductivity of (Bi2O3)0.75(Dy2O3)0.25 ceramics with grain sizes from the nano to the micro scale

“…This decrease in ion conductivity could be due to an increase in the volume of the grain boundary with the reduction of grain size, which may become the limiting factor below 100 nm. The same effect was also observed in yttria doped zirconia ceramics, which exhibits the same fluorite structure as δ-Bi 2 O 3 [35]. According to Peters et al, space charge effect will be pronounced only in materials with low concentrations of mobile point defects [36].…”

Electrochemical characterization of nanostructured zirconias

“…The role of the microstructure, such as grain size, grain boundaries, pores and second phases, on the electrolyte conductivity has been much debated in recent years. Large discrepancies between the published results are observed [5][6][7][8]. It should be pointed out that the key difference between the published results is the manner in which the nanocrystalline samples were prepared as bulk or thin films, since the blocking effect appears to be mainly controlled by the density of the grain boundaries.…”

“…Crystalline phases were also identified by Raman spectroscopy (Jobin Yvon T64000 or Dilor XY), using the excitation line of an argon ion laser (λ = 514 nm). Raman spectroscopy is very helpful in studying the microscopic nature of nanocrystalline materials and various results are available in literature [8,[24][25][26][27]. X-ray diffraction patterns (Fig.…”

“…Indeed, an enhancement of about 2 orders of magnitude was measured (i) by Mondal et al [5] in nearly pure tetragonal zirconia ceramics with d g of 25-50 nm, (ii) by Kosacki [11] in 8YSZ thin films with d g of 20 nm. From Boulfrad et al [8], the grain boundaries were found to be intrinsically resistive even for nanostructured ceramics with d g less than 100 nm. Although the specific resistivity of the blocking contribution decreases with decreasing grain size, it remains about 100 times higher than the bulk resistivity.…”