Structural Evolution and Electrical Properties of Sc₂O₃‐Stabilized ZrO₂ Aged at 850°C in Air and Wet‐Forming Gas Ambients

Abstract

X-ray diffraction (XRD) and electron microscopy investigations have been performed on Sc 2 O 3 -stabilized ZrO 2 as-sintered and after aging in air or in wet-forming gas at 8501C for 1000 h. Some tetragonal to monoclinic transformation had occurred in the near-surface regions of 4 mol% Sc 2 O 3 samples after aging; the phase transition was more severe for samples aged in the forming gas ambient. A decrease of B20% in electrical conductivity accompanied the aging. In 6 mol% Sc 2 O 3 samples, although no cubic to tetragonal transformation was detected, both the electrical conductivity and the activation energy for ionic conductivity decreased significantly during aging. Ten mole percent Sc 2 O 3 samples did not show appreciable change in electrical conductivity due to aging, although some near-surface cubic to rhombohedral transformation did occur. Sharpening of the (400) t XRD peak of Sc 2 O 3 -stabilzed tetragonal ZrO 2 accompanies the change(s) in the electrical conductivity. M. P. Paranthaman-contributing editor

Structure and conductivity of yttria and scandia‐doped zirconia crystals grown by skull melting

“…Ion conductivity of YSZ depends on yttria content and yields the highest ion conductivity at 8 to 9 mol% Y 2 O 3 . [8][9][10] One method to improve the properties of the electrolyte materials, such as to stabilize the cubic modification, to suppress conductivity degradation is the introduction of second dopant (co-dopant) in addition to Sc 3+ into the electrolyte structure. 4 The cubic fluorite-type phase of scandia stabilized zirconia (ScSZ) shows the highest conductivity among all zirconia solid solutions.…”

Comparative studies on synthesis of nanocrystalline Sc2O3–Y2O3 doped zirconia (SYDZ) and YSZ solid solution via modified and classic Pechini method

“…It should be noted that in order to clearly observe the tetragonal splitting in the entire 2h region in yttria-containing zirconia ceramics, the material must be sintered above 1100 uC. 9,10 In comparison to this sample, the SYDZ nanocrystals, synthesized with a Sc 2 O 3 : Y 2 O 3 mole ratio equal to 3.5 : 0.5, show dissimilar HRTEM images and SAED patterns. 29,30 Fig.…”

“…[4][5][6] Tetragonal zirconia can be used as an effective catalyst due to its unique amphoteric characteristics and redox properties. [6][7][8][9] The 'non-transformable' metastable tetragonal YSZ phase (called t9) is remarkably resistant and does not undergo the transformation to the monoclinic phase under stresses. This hardening mechanism is due to the transformation of the tetragonal phase into the monoclinic phase, which implies a volume change associated with pseudoplasticity.…”

“…12 They showed that a higher conductivity could be obtained with SYDZ than YSZ and ScSZ (scandia stabilized zirconia). 9 For this reason, based on wet chemical routes, several increasingly important alternatives make the synthesis of zirconia-based solid solutions at mild temperatures possible. One approach was taken by Jones 13 who sought to combine the stabilizing efficiency of Y 2 O 3 with the vanadate-corrosion resistance of Sc 2 O 3 .…”

Photoluminescence properties of scandia-stabilized zirconia

“…Sc 2 O 3 -stabilized ZrO 4 (scandiastabilized zirconia, ScSZ) is one of the viable candidate to replace Y 2 O 3 -stabilized ZrO 4 (yttria-stabilized zirconia, YSZ), and its structural properties have been actively investigated [1].…”