光谱学与光谱分析, 2020, 40 (3): 950, 网络出版: 2020-03-25  

XRD-Rietveld全谱拟合法应用于土壤样品物相定量的准确性检验: 模拟实验与方法对比

Accuracy Testing of Soil Mineral Quantification by XRD-Rietveld Full-Spectrum Fitting Method: Simulation Experiments and Comparison with Traditional Method
作者单位
1 广西有色金属隐伏矿床勘查及材料开发协同创新中心, 桂林理工大学, 广西 桂林 541004
2 桂林理工大学地球科学学院, 广西 桂林 541004
3 广西壮族自治区国土资源厅, 广西 南宁 530028
4 广西地质调查院, 广西 南宁 530023
摘要
XRD-Rietveld全谱拟合法(简称Rietveld法)是一种在材料学领域被广泛应用于解决复杂多相混合物体系物相定量问题的先进技术方法。 将该物相定量方法跨学科引入地学, 理论上有助于提高地学样品矿物物相分析的精确度。 然而, 在该技术方法的实际应用中, 当前有两个基础问题需要解决, 一是Rietveld技术方法对地学样品的适用性有待检验, 二是分析结果的可靠性还缺乏实验评价依据。 针对这两个问题, 本研究基于自然界土壤中常见的矿物组合特征, 配置了三组已知矿物成分含量的土壤模拟样品(石英+赤铁矿1∶1二相混合土壤模拟样; 石英+高岭石1∶1二相混合土壤模拟样; 石英+高岭石+蒙脱石1∶1∶1三相混合土壤模拟样), 并以这些样品为例, 开展了Rietveld法物相定量分析与计算。 分析表明, 利用Rietveld法, 能获得土壤模拟样品良好的XRD拟合谱线, 拟合谱(ycalc)与测试谱(yobs)匹配度高, 拟合值(Rwp<15%)、 拟合期望(Rexp<15%)和拟合优度(gof<5)等参数指标均符合矿物物相定量计算要求。 三组土壤模拟样品的Rietveld矿物物相计算值与真实值的误差仅为0.63%, 1.46%和1.03%, 指示该方法对土壤模拟样品的矿物物相定量结果能有效逼近真实成分比例, 且显著优于传统的内标法分析结果。
Abstract
The XRD-Rietveld full-spectrum fitting method (Rietveld method) is an advanced technical method that is widely used in the field of materials science to solve the quantification issue of multiphase mixture samples. Theoretically, the Rietveld method could be applied in the geosciences field, and it can help geologists to get a better result in the analysis of mineral quantification of geoscience samples. However, in practical applications, there are several basic problems needing to be solved, especially concerning the applicability of the method itself and the reliability of analysis data. Regarding to these issues, taking soil samples for example, a simulation experiment was conducted in this study. Prior to application of the Rietveld method, three sets of simulated soil samples were prepared firstly according to the common knowledge of natural soil mineralogy, including quartz+hematite 1∶1 mixture sample, quartz+kaolinite 1∶1 mixture sample and quartz+kaolinite+montmorillonite 1∶1∶1 mixture sample. Using the Rietveld method, we obtained good XRD fitting lines for all simulated soil samples. Specifically, some important indices, including fitting value (Rwp<15%), fitting expectation (Rexp<15%) and goodness of fit (gof<5), could all meet the requirements of applying the Rietveld method. Also, the Rietveld-based mineral quantification data were very close to their real values, with errors only 0.63%, 1.46% and 1.03% for three samples respectively. This result indicated that the application of Rietveld method to quantify the soil mineral composition is feasible and reliable, which can get better results than the traditional “internal standard” method.

付伟, 彭召, 罗鹏, 覃建勋, 冯洋洋. XRD-Rietveld全谱拟合法应用于土壤样品物相定量的准确性检验: 模拟实验与方法对比[J]. 光谱学与光谱分析, 2020, 40(3): 950. FU Wei, PENG Zhao, LUO Peng, QIN Jian-xun, FENG Yang-yang. Accuracy Testing of Soil Mineral Quantification by XRD-Rietveld Full-Spectrum Fitting Method: Simulation Experiments and Comparison with Traditional Method[J]. Spectroscopy and Spectral Analysis, 2020, 40(3): 950.

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