变色氟碳铈矿的化学成分及谱学特征

张龙博; 张倩

doi:10.15964/j.cnki.027jgg.2019.05.003

变色氟碳铈矿的化学成分及谱学特征

张龙博,
张倩^,

中国地质大学珠宝学院，湖北武汉 430074

基金项目:

中央高校基本科研业务费专项资金项目 CUGL170218

中国地质大学(武汉)珠宝检测技术创新中心项目

详细信息

作者简介:
张龙博(1995-)，男，硕士研究生，主要从事宝石学方向研究

通讯作者:
张倩(1986-)，女，讲师，主要从事宝石学及矿物学方向的研究工作。E-mail: qianzhang@cug.edu.cn

中图分类号: TS93
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出版历程
- 收稿日期: 2019-03-18
- 刊出日期: 2019-08-31

Chemical Composition and Spectral Characteristic of Colour-Change Bastnäsite(Ce)

ZHANG Longbo,
ZHANG Qian^,

Gemmological Institute, China University of Geosciences, Wuhan 430074, China

摘要

摘要: 氟碳铈矿是一种稀少的宝石品种, 为稀土氟碳酸盐矿物，可具有变色效应。采用电子探针、傅里叶变换红外光谱仪、激光拉曼光谱仪及紫外-可见分光光度计测试了变色氟碳铈矿样品的化学成分及谱学特征，并对其颜色及变色效应进行了探究。结果表明，氟碳铈矿样品中主要稀土元素阳离子有Ce³⁺、La³⁺、Nd³⁺、Pr³⁺和Sm³⁺，2颗氟碳铈矿样品的化学式分别为(Ce_0.50La_0.27Nd_0.16Pr_0.05Sm_0.02)(CO₃)F和(Ce_0.47La_0.24Nd_0.20Pr_0.05Sm_0.03)(CO₃)F；中红外光谱吸收峰主要由CO₃^2-的振动引起，近红外光谱的吸收峰与CO₃^2-、Pr³⁺、Nd³⁺和Sm³⁺有关；拉曼光谱的吸收峰主要与CO₃^2-的振动以及晶格中的F^-有关；紫外-可见吸收光谱的大部分吸收峰由Nd³⁺的4f-4f电子跃迁导致。结合电子探针分析结果，氟碳铈矿的颜色由Nd³⁺引起。根据576，740 nm附近两个透过率几乎相等的强吸收峰推断，氟碳铈矿的变色效应也是由Nd³⁺引起。
- 氟碳铈矿 /
- 稀土元素 /
- 谱学特征 /
- 变色效应
Abstract: Bastnäsite(Ce), a cerium-dominant rare-earth element fluorocarbonate, is a rare gemstone which could display alexandrite effect. In this paper, the authors studied the chemical compositions and spectral characteristics of bastnäsite samples by means of electron microprobe, Fourier transform infrared spectroscopy, Raman spectroscopy and ultraviolet-visible spectroscopy. The results of electron microprobe indicated that Ce、La、Nd、Pr and Sm are the main rare-earth elements in bastnäsite. The structural formulas calculated by the electron microprobe data of two samples are (Ce_0.50La_0.27Nd_0.16Pr_0.05Sm_0.02)(CO₃)F and (Ce_0.47La_0.24Nd_0.20Pr_0.05Sm_0.03)(CO₃)F respectively. The middle-infrared bands are assigned to the different vibrations of CO₃^2- and the near-infrared bands are associated with CO₃^2-, Pr³⁺, Nd³⁺or Sm³⁺. Raman bands are associated with various CO₃^2- vibrations and lattice modes involving F^-. The results of UV-Vis absorption spectroscopy showed that most of the bands are induced by 4f-4f electronic transition of Nd³⁺. Based on the results of electron microprobe analysis, it is considered that the colour of bastnäsite is produced by Nd³⁺. Since the two strong absorption peaks near 576 nm and 740 nm have approximately equal transmission rate, it is inferred that the alexandrite effect of bastnäsite is caused by Nd³⁺.
- bastnäsite /
- rare-earth element /
- spectral characteristic /
- alexandrite effect

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图 1 氟碳铈矿样品在白炽灯(左)和日光灯(右)下的照片

Figure 1. Photos of bastnäsite samples under incandescent light (left) and daylight (right)

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图 2 氟碳铈矿样品的中红外光谱

Figure 2. Mid-IR spectra of bastnäsite samples

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图 3 氟碳铈矿样品的近红外光谱

Figure 3. NIR spectra of bastnäsite samples

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图 4 氟碳铈矿样品的拉曼光谱

Figure 4. Raman spectra of bastnäsite samples

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图 5 氟碳铈矿样品的紫外-可见吸收光谱

Figure 5. UV-Vis spectra of bastnäsite samples

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表 1 氟碳铈矿样品的电子探针测试结果及化学式计算

Table 1 EPMA data and calculated structural formula of bastnäsite samples

氧化物	质量分数(w_B/%)		元素	阳离子数
氧化物	样品B1	样品B2	元素	样品B1	样品B2
P₂O₅	0.02	0.02	P	0.000 8	0.000 6
La₂O₃	20.48	18.53	La	0.270 7	0.244 7
CaO	0.03	0.02	Ca	0.001 2	0.000 8
Ce₂O₃	37.94	35.82	Ce	0.497 7	0.469 6
Y₂O₃	0.04	0.05	Y	0.000 8	0.001 0
Nd₂O₃	12.51	15.59	Nd	0.160 1	0.199 3
SiO₂	0.02	0.02	Si	0.001 0	0.000 8
Gd₂O₃	0.05	0.21	Gd	0.000 6	0.002 5
Sm₂O₃	1.35	2.24	Sm	0.016 7	0.027 6
Eu₂O₃	0.08	0.15	Eu	0.001 0	0.001 9
Yb₂O₃	0.01	0.03	Yb	0.000 2	0.000 3
Pr₂O₃	3.61	3.76	Pr	0.047 1	0.049 1
CoO	0.05	0.04	Co	0.001 4	0.001 2
TiO₂	0.01	0.02	Ti	0.000 2	0.000 6

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参考文献(14)

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