天然钻石和合成钻石的光谱学特征研究

Comparative study on the spectralcharacteristics of natural diamond and synthetic diamond

目前,市场上90%~98%的天然无色钻石通常为Ia型(包括IaA、IaAB、IaB型),无色合成钻石主要为II型(包括IIa型、IIb型)。通过紫外荧光灯、宝石显微镜、傅里叶变换红外光谱(FTIR)、紫外-可见-近红外(UV-Vis-NIR)吸收光谱结合显微共焦激光拉曼光谱对天然钻石、高温高压(HTHP)法合成钻石和化学气相沉淀(CVD)法合成钻石进行光谱学特征研究,并对拉曼光谱1335 cm^(-1)谱峰进行洛伦兹拟合,得到半高全宽值,对半高全宽值进行单因素方差分析。结果表明:天然钻石长波荧光强于短波,合成钻石的短波荧光强于长波;天然钻石内部可见云状物、浅色晶体包体、深色包体,HTHP合成钻石内部可见Fe、Ni金属触媒包体,CVD合成钻石内部可见点状包体,HTHP样品具有磁性;红外吸收光谱显示,天然钻石在1179 cm^(-1)、1282 cm^(-1)、1365 cm^(-1)处有明显吸收峰,属于IaAB型;合成钻石在1332~1100 cm^(-1)无明显氮相关吸收,属于II型;UV-Vis-NIR光谱显示,天然钻石存在415 nm(N3)吸收峰,而合成钻石无此吸收峰;天然钻石和合成钻石的拉曼位移一致,半高全宽存在显著差异,天然钻石的半高全宽均在6.0 cm^(-1)以上,合成钻石的半高全宽值均在6.0 cm^(-1)以下,可为鉴别天然钻石和合成钻石提供理论依据。

Currently,90%to 98%of the natural colorless diamonds on the market are usually Ia type(Includes IaA,IaAB,IaB),colorless synthetic diamonds are mainly II type(includes IIa,IIb).The spectral characteristics of natural diamond,synthetic diamond at high temperature and high pressure(HTHP)and chemical vapor deposition(CVD)were studied by using ultraviolet fluorescent lamp,Gem Microscope,Fourier transform infrared(FTIR),ultraviolet visible near infrared absorption spectrum(UV-Vis-NIR)and confocal laser Raman spectroscopy.The Raman spectra of 1335 cm^(-1) were fitted by Lorentz,and the FWHMt was obtained.The results were analyzed by one-way ANOVA.The results show that the long wave fluorescence of natural diamond is stronger than that of short wave,and that of synthetic diamond is stronger than that of long wave.Cloud like inclusions,light crystalline inclusions and dark inclusions can be seen in natural diamond,Fe、Ni metal catalyst inclusions can be seen in high temperature and high pressure synthetic diamond,and point inclusions can be seen in CVD synthetic diamond.High temperature and high pressure samples are magnetic.The infrared absorption spectra show that the natural diamond has obvious absorption peaks at 1179 cm^(-1),1282 cm^(-1) and 1365 cm^(-1),belonging to IaAB type;the synthetic diamond has no obvious nitrogen related absorption at 1332-1-1100 cm^(-1),belonging to type II.UV-Vis-NIR spectra show that natural diamond has an absorption peak of 415 nm(N3),while synthetic diamond has no such absorption peak.The Raman shifts of natural diamond and synthetic diamond are the same.The full width at half height of natural diamond is more than 6.0 cm^(-1),and that of synthetic diamond is less than 6.0 cm^(-1).It provides a theoretical basis for the identification of natural diamond and synthetic diamond.