Effect of Aging on Yttria‐Stabilized Zirconia: II. A Study of the Effect of the Microstructure on Conductivity

Abstract

Microstructural changes in yttria-stabilized zirconia with aging were investigated by X-ray diffraction, high resolution transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy under TEM, and electron diffraction. First, various microstructural changes reported in the literature as the causes of the decrease in conductivity were carefully examined. As a result, almost all of them proved not to be the direct cause. Therefore, the changes with aging were analyzed mainly by calling attention to a characteristically broad area that appears on the left shoulder of the X-ray diffraction peaks as well as the superlattice reflections and diffuse scattering seen on electron diffraction patterns, and the relationship between microstructural changes and conductivity was clarified. It is concluded that various phenomena due to aging at relatively lower temperatures are caused by short range ordering of oxygen ion vacancies, which occurs in order to relax the anisotropy of periodical lattice distortion. We also studied changes in microstructures occurring with changing dopant concentrations and concluded that the changes in microstructures responsible for the decrease in conductivity associated with increasing dopant concentration are caused by short range ordering of oxygen ion vacancies in order to relax the anisotropy in strain fields, similarly to those with aging. InfroductionA number of microstructural studies of stabilized zirconia have been conducted using various methods, including neutron diffraction and scattering,1'6 X-ray diffraction and scattering7-9 electron diffraction,10'14 and transmission electron microscopy (TEM).15"8 Because partially stabilized zirconia is a useful material with incomparably high toughness due to stress-induced phase transformation, many microstructural studies of it have been conducted, examining phase transformations, characterizing lattice defects,

Effect of Aging on the Electrochemical Performance of LSM-YSZ Cathodes

“…[30][31][32]36 As shown in Figure 2(a), the hump is not present in any of the diffractograms corresponding to the aged samples. The shrinking of the HLS after annealing or aging within the 600-1000 ºC range has also been observed by other authors and attributed to a short range ordering of oxygen ion vacancies to relax the anisotropy of the lattice distortions, 28 or to the reverse transformation of the rhombohedral phase.…”

“…The low intensity peak situated at 2Θ ≈ 29.4° and resembling a "hump on the left shoulder" (HLS) 28 was also found in the 0 h sample (see Figure 2(b)). This feature was proposed to be caused by the anisotropy of lattice distortion, 28,29 by the formation of a rhombohedral phase induced by stress, [30][31][32][33][34] by the formation of low-dimensional structures after surface segregation, 35 and by grinding or polishing.…”

“…This feature was proposed to be caused by the anisotropy of lattice distortion, 28,29 by the formation of a rhombohedral phase induced by stress, [30][31][32][33][34] by the formation of low-dimensional structures after surface segregation, 35 and by grinding or polishing. [30][31][32]36 As shown in Figure 2(a), the hump is not present in any of the diffractograms corresponding to the aged samples.…”

Nano-structure design of doped ceria solid electrolytes for intermediate temperature operation of solid oxide fuel cell

“…Also influence of the diffuse scattering of the stabilized ZrO 2 on long time aging was observed by TEM. 31 Those analysis suggest that the diffuse scattering is appeared by the short range ordering of oxygen vacancy in the fluorite lattice. It would be attributable to phase separation of tetragonal zirconia and cubic zirconia at micro-scale.…”

Nano-structure design of doped ceria solid electrolytes for intermediate temperature operation of solid oxide fuel cell

“…Also influence of the diffuse scattering of the stabilized Zr0 2 on long time aging was observed by TEM. 31 Those analysis suggest that the diffuse scattering is appeared by the short range ordering of oxygen vacancy in the fluorite lattice. It would be attributable to phase separation of tetragonal zirconia and cubic zirconia at micro-scale.…”