Subsurface segregation of yttria in yttria stabilized zirconia
Subsurface segregation of yttria in yttria stabilized zirconia
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DOI：
10.1063/1.1499748
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发表时间：
2002-09-15
影响因子：
3.2
通讯作者：
Weppner, W
中科院分区：
文献类型：
--
作者：
de Ridder, M;van Welzenis, RG;Weppner, W
采用低能离子散射（LEIS）技术，研究了在300 ~ 1600 ℃温度范围内煅烧的3 ~ 10mol%多晶氧化钇稳定氧化锆（YSZ）的偏析行为。为了能够分离Y和Zr LEIS信号，已经使用同位素富集的（ZrO 2）-Zr-94代替天然氧化锆制备了YSZ样品。样品是在低温下通过特殊的沉淀方法制备的。向最外表面层的偏析主要由杂质控制。增加的杂质水平仅限于第一层，这强调了使用LEIS进行本研究的重要性。对于1000 ℃或更高的温度，杂质Na、Si和Ca的氧化物甚至完全覆盖表面。因此，像具有YSZ电解质和大约1000 ℃的工作温度的固体氧化物燃料电池这样的设备的性能将受到这些杂质的强烈阻碍。只有当总杂质体积浓度可以降低到10 ppm水平以下时，杂质的减少才能有效防止在表面的积累。由于杂质的存在，氧化钇不能积聚在最外层。与一般的看法相反，它是在次表层，而且浓度比以前报告的值高得多。Y_2O_3和ZrO_2的界面自由能之差为-21+/-3kJ/mol。(C)2002年美国物理学会。
The segregation behavior in 3 and 10 mol % polycrystalline yttria stabilized zirconia (YSZ), calcined at temperatures ranging from 300 to 1600 degreesC, is characterized using low-energy ion scattering (LEIS). In order to be able to separate the Y and Zr LEIS signals, YSZ samples have been prepared using isotopically enriched (ZrO2)-Zr-94 instead of natural zirconia. The samples are made via a special precipitation method at a low temperature. The segregation to the outermost surface layer is dominated by impurities. The increased impurity levels are restricted to this first layer, which underlines the importance of the use of LEIS for this study. For temperatures of 1000 degreesC and higher, the oxides of the impurities Na, Si, and Ca even cover the surface completely. The performance of a device like the solid oxide fuel cell which has an YSZ electrolyte and a working temperature around 1000 degreesC, will, therefore, be strongly hampered by these impurities. The reduction of impurities, to prevent accumulation at the surface, will only be effective if the total impurity bulk concentration can be reduced below the 10 ppm level. Due to the presence of the impurities, yttria cannot accumulate in the outermost layer. It does so, in contrast to the general belief, in the subsurface layer and to much higher concentrations than the values reported previously. The difference in the interfacial free energies of Y2O3 and ZrO2 is determined to be -21+/-3 kJ/mol.(C) 2002 American Institute of Physics.