Scandia doping

For a given composition and a given charge cation, the conductivity increases as the radius of the dopant cation approaches that of zirconium. Thus, scandia-doped zirconia shows the best conductivity (rSc3+ = 0.81 A and zZr4+ = 0.8 A) in this family. 

Yttria stabilized zirconia (YSZ), which has been used extensively in SOFC s, shows a conductivity of 0.14 S/cm at 1000 °C. Scandia doped zirconia (SSZ) has a higher conductivity and at 780 °C its value corresponds to that of YSZ at 1000 °C. In Fig. 3, the thickness of the electrolyte showing a resistance of 0.15 Ocm is shown on the right side of the vertical axis. The... 

Scandia doped zirconia (SDZ) is quite attractive as the electrolyte for SOFC s, especially for the intermediate temperature (600-800 °C) SOFC s. The long-term stability was not clarified before Yamamoto et al. reported the aging effect by annealing at higher temperatures [27]. Zr02 with 8 mol %... 

It can be seen from the figure that, over the temperature range from 1000°C to 400 C, the last two electrolytes have a markedly higher conductivity, than yttria-doped zirconia. It can also be seen from the figure that scandia-doped zirconia has a markedly higher conductivity than yttria-doped zirconia, but it is very rarely used on account of its high price. 

The SOEC consists of relatively inexpensive materials and may be produced using low-cost processes. Electrolytes are most often yttria-stabUized zirconia (YSZ) of composition Zro.84Yo.i6O1.92, often called 8YSZ, but recently scandia doping or co-doping of the zirconia has become popular in both SOEC and SOEC... 

During the past decades, many oxide formulations have been extensively examined in the search for candidate SOFC electrolyte materials. Zirconia-based compositions are still the best electrolytes at present owing to their good stability under reducing atmospheres, low electronic conductivity, and acceptable oxide ion conductivity above 800°C. The recent trend of SOFC development is to operate at lower temperatures. The lowest operation temperature limit of the cell, for thin YSZ electrolytes, is estimated to be about 700°C from YSZ conductivity and mechanical property data. Scandia-doped zirconia, which shows a higher conductivity than that of YSZ, could be preferred at temperatures below 700°C, if the cost of scandia was acceptable. 

The stack electrolytes are scandia-stabilised zirconia, about 140 (im thick. The air-side electrodes (anode in the electrolysis mode) are a strontium-doped manganite. The electrodes are graded, with an inner layer of manganite/zirconia ( 13 pm) immediately adjacent to the electrolyte, a middle layer of pure manganite ( 18 pm), and an outer bond layer of cobaltite. The steam/hydrogen electrodes (cathode in the electrolysis mode) are also graded, with a nickel-zirconia cermet layer ( 13 pm) immediately adjacent to the electrolyte and a pure nickel outer layer ( 10 pm). 

Serivalsatit K, Ballato J (2010) Submicrometer grain-sized transparent erbium-doped scandia... 

Nomura, K., Mizutani, Y., Kawai, M., Nakamura, Y., and Yamamoto, O. (2000). Aging and Raman scattering study of scandia and yttria doped zirconia. Solid State Ionics 132 ... 

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