Lead diffusion in titanite and preliminary results on the effects of radiation damage on Pb transport
Lead diffusion in titanite and preliminary results on the effects of radiation damage on Pb transport
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DOI：
10.1016/0009-2541(93)90253-f
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发表时间：
1993-11
期刊：
影响因子：
3.9
通讯作者：
D. Cherniak
中科院分区：
文献类型：
--
作者：
D. Cherniak
采用两种不同的方法引入扩散剂，测量了铅在天然钛酸盐中的扩散：（1）Pb离子注入;（2）将晶体浸入PbS粉末储存器中。在这两组实验中，卢瑟福背散射光谱法（RBS）被用来获得浓度分布，然后拟合适当的解决方案的扩散方程。实验使用PbS粉末源，在650-1027° C的温度范围内运行，定义了阿耳忒弥斯关系：D= 1.11+ 1.18− 0.57 exp− 78.5±2.7（kcal mol− 1）RT（cm 2 s− 1），扩散平行于（100）平面。扩散系数没有显着影响的取向或预退火处理的差异。相比之下，离子注入实验偏离了简单的线性阿耳忒弥斯行为，高温数据（850-950° C）显示出与上述关系的良好一致性，但低温数据（600-800° C）显示出增强的扩散率和降低的活化能（19 kcal mol− 1）。这些结果表明，由离子注入引起的辐射损伤在高温下修复，从而导致两个数据集的协议。在较低的温度下，晶格修复相对于扩散退火的持续时间进行得慢得多，导致已经变成非晶的材料的典型扩散系数升高。与磷灰石和锆石的早期工作进行比较，发现在这些矿物之间，磷灰石的修复速度更快，锆石的修复速度更慢，对于相同的注入剂量和类似的退火条件。这种差异在很大程度上是结构和成分特征的函数，影响的积累和修复的速度在每个mineral. The结果在这里提出的铅运输和解释同位素比值在自然辐射损伤的矿物，离子注入产生的损害相当于从α-反冲。
Lead diffusion has been measured in natural titanite using two different methods to introduce the diffusant:(1) implantation of Pb ions; and (2) immersion of the crystals in a PbS powder reservoir. In both sets of experiments, Rutherford backscattering spectrometry (RBS) was used to obtain concentration profiles, which were then fit with appropriate solutions to the diffusion equation. Experiments using the PbS powder source, run over the temperature range 650–1027° C, define the Arrhenius relationship: D= 1.11+ 1.18− 0.57 exp− 78.5±2.7 (kcal mol− 1) RT (cm 2 s− 1) for diffusion parallel to the (100) plane. Diffusivities are not significantly affected by orientation or differences in preannealing treatment. The ion implantation experiments, in contrast, deviate from simple linear Arrhenius behavior, with the high-temperature data (850–950° C) displaying good agreement with the above relation but the lower-temperature data (600–800° C) exhibiting enhanced diffusivities and a lowered activation energy (19 kcal mol− 1). These results suggest that radiation damage induced by the ion implantation is repaired at high temperatures, thus leading to agreement of the two data sets. At lower temperatures, lattice repair proceeds much more slowly in relation to the duration of the diffusion anneal, resulting in elevated diffusion coefficients typical of materials that have become amorphous. A comparison with earlier work on apatite and zircon places the rate of repair of implantation-induced damage in titanite between these minerals, with apatite exhibiting a more rapid rate of repair and zircon a much slower rate for the same implant dose and similar annealing conditions. This difference is largely a function of structural and compositional characteristics that affect the rate of accumulation and repair of damage in each mineral. The results presented here may have important implications for Pb transport and interpretation of isotope ratios in naturally radiation-damaged minerals, as ion implantation produces damage comparable to that resulting from α-recoil.