Ion beam irradiation in La2Zr2O7-Ce2Zr2O7 pyrochlore
Ion beam irradiation in La2Zr2O7-Ce2Zr2O7 pyrochlore
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DOI：
10.1016/j.nimb.2004.01.007
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发表时间：
2004-06-01
影响因子：
1.3
通讯作者：
Ewing, RC
中科院分区：
文献类型：
--
作者：
Lian, J;Wang, LM;Ewing, RC
一般来说，锆酸盐烧绿石不会经历辐射诱导的从结晶态到非晶态的转变，而是无序到缺陷萤石结构类型。因此，由于 Gd2Zr2O7 的辐射“稳定性”，Gd2Zr2O7 已被提议作为一种用于固定钚的核废料形式。相比之下，La2Zr2O7可以通过1.5 MeV Xe+离子辐照（室温下约5.5 dpa）实现非晶化，并且临界非晶化温度较低（约310 K）。在这项研究中，我们提供了固溶体中成分的离子束辐照数据：(La1-xCex)(2)Zr2O7 (x = 0, 0.1, 0.2, 1)。由于电荷和尺寸相似，Ce 被用作 Pu 的类似元素。 La2Zr2O7可以通过1.0 MeV Kr+离子在25和293 K、剂量分别类似于1.19和类似于3.42 dpa的辐照下非晶化，证实La2Zr2O7对离子辐照诱导的非晶化敏感。在锆酸镧烧绿石结构中添加10 mol% Ce后，在室温下没有观察到离子辐照引起的非晶化。 (La0.9Ce0.1)(2)Zr2O7 在 25 K 时的临界非晶化剂量与 3.55 dpa 相似，随着 Ce 含量的增加，需要更高的剂量（类似于 5.20 dpa）才能在 25 K 下完全非晶化 (La0.8Ce0.2)(2)Zr2O7。Ce2Zr2O7 在 25 K 时没有发生非晶化。 a.剂量类似于7 dpa。这些结果表明，在La2Zr2O7结构中添加Ce提高了La2Zr2O7废物形式在辐射环境中的稳定性，这可能归因于A位中阳离子的平均半径减小，这是由于与La3+（0.116 nm）相比，Ce3+（0.114 nm）和Ce4+（0.097 nm）的离子半径较小。在最终转变为无序萤石结构之前，观察到离子束诱导的阴离子无序烧绿石。还使用电子能量损失谱 (EELS) 研究了具有不同平均 A 位阳离子尺寸和价态的 Ce 掺杂 La2Zr2O7 烧绿石在离子辐照下的局部结构演化。 (C) 2004 Elsevier B.V. 保留所有权利。
Generally, zirconate pyrochlores do not experience a radiation-induced transformation from the crystalline-to-amorphous state, but rather disorder to a defect fluorite structure-type. Thus Gd2Zr2O7 has been proposed as a nuclear waste form for the immobilization of plutonium because of its radiation "stability". In contrast, La2Zr2O7 can be amorphized by a 1.5 MeV Xe+ ion irradiation (similar to5.5 dpa at room temperature), and the critical amorphization temperature is low (similar to310 K). In this study we present data on ion beam irradiations of compositions in the solid solution: (La1-xCex)(2)Zr2O7 (x = 0, 0.1, 0.2, 1). Ce is used as an analogue element for Pu because of similarities in charge and size. La2Zr2O7 can be amorphized by a 1.0 MeV Kr+ ion irradiation at 25 and 293 K at doses of similar to1.19 and similar to3.42 dpa, respectively, confirming that La2Zr2O7 is Susceptible to ion irradiation-induced amorphization. With the addition of 10 mol% Ce in lanthanum zirconate pyrochlore structure, no ion irradiation-induced amorphization has been observed at room temperature. The critical amorphization dose for (La0.9Ce0.1)(2)Zr2O7 at 25 K is similar to3.55 dpa, and with increasing Ce-content, a higher dose (similar to5.20 dpa) is required to fully amorphize (La0.8Ce0.2)(2)Zr2O7 at 25 K. No amorphization occurred for Ce2Zr2O7 at 25 K at a. dose of similar to7 dpa. These results suggest that the addition of Ce into the La2Zr2O7 structure increases the stability of the La2Zr2O7 waste form in a radiation environment, which may be attributed to the decreasing average radius of cations in the A-site, resulting from the smaller ionic radii of Ce3+ (0.114 nm) and Ce4+ (0.097 nm) as compared to La3+ (0.116 nm). An ion beam-induced anion-disordered pyrochlore was observed prior to the final transformation to a disordered fluorite structure. The local structural evolution upon ion irradiation was also investigated for Ce-doped La2Zr2O7 pyrochlores with different average A-site cation sizes and valence states using electron energy-loss spectrometry (EELS). (C) 2004 Elsevier B.V. All rights reserved.