山东产大颗粒高温高压合成钻石的多种谱学方法研究

Multi-Spectroscopy Studies on Large Grained HPHT Synthetic Diamonds from Shandong, China

山东济南中乌新材料有限公司利用六面顶油压机生产出大颗粒钻石,为了掌握这些合成钻石的品质及与天然钻石的区分方法,采用宽频诱导发光光谱仪(GV5000)、红外光谱仪、钻石特征光谱检测仪(PL5000)、激光诱导击穿光谱仪和X射线能谱仪,对该公司生产的225粒无色、蓝色和黄色高温高压(HPHT)合成钻石进行检测,并与天然钻石对比。HPHT合成钻石样品的晶形以(111)晶面和(100)晶面共存的聚形为主导。原石切磨成圆钻形成品的出成率在20%~67%之间,净度级别为VVS—P,颜色级别为D—H。通过GV5000分析,三种颜色样品均可观察到立方八面体生长结构发光图案,无色HPHT合成钻石为强蓝色荧光和磷光,发光峰位于495nm,与晶格中的顺磁氮有关;蓝色HPHT合成钻石为蓝-绿蓝色荧光和蓝色磷光,发光峰位于501nm,与晶格中的顺磁氮、硼有关;黄色HPHT合成钻石为弱绿色荧光和磷光,显示556和883nm Ni^+相关发光峰,这些特征可与天然钻石相区分。红外光谱分析表明,无色HPHT合成钻石在1332~1100cm^-1无明显氮相关吸收,在2802cm^-1有B^0相关吸收,为含有少量硼的Ⅱa型;蓝色HPHT合成钻石位于1294cm^-1有与B-相关的强吸收,归属为Ⅱb型;黄色HPHT合成钻石位于1130和1344cm-1有与孤氮相关的明显吸收,归属为Ⅰb型。PL5000光致发光光谱显示,三种颜色HPHT合成钻石可检测到659,694,707,714和883nm等镍相关缺陷发光峰。相比之下,无色和黄色天然钻石通常为Ⅰa型,具有1282和1175cm^-1等聚合氮的红外光谱吸收,光致发光光谱通常可检测到415nm(N3)零声子线,由孤氮、硼和镍等缺陷导致的光谱特征极为罕见。因此,红外光谱和光致发光光谱特征可作为重要的鉴别依据。激光诱导击穿光谱仪检测到无色HPHT合成钻石的出露包裹体主要成分为Fe。X射线能谱分析显示,对于含包裹体较多的样品,无色和蓝色HPHT合成钻石可检测到Fe,黄色HPHT合成钻石可检测到Fe和Ni,为其中包裹体的成分,这可作为HPHT合成钻石鉴定性特征。综上所述,通过GV5000超短波紫外荧光和磷光测试,配合红外光谱和光致发光光谱特征,结合包裹体成分特征,可以有效区分该研究的合成钻石和天然钻石。

Large grained synthetic diamond single crystals have been synthesized by international advanced six-sided top hydraulic press by Ji’nan Zhongwu New Material Co.Ltd.To characterize the quality of these synthetic diamonds and establish the identification principles,225 large colorless,yellow,and blue HPHT synthetic diamonds produced by the company were studied by stereoscopic microscope,multi-spectral induced luminescence imaging system(GV5000),infrared absorption spectrometer(FTIR),diamond photoluminescence spectrometer(PL5000),laser induced breakdown spectrometer(LIBS)and X-ray energy dispersive spectrometer(EDS)and compared to natural diamonds.The crystal morphology of HPHT synthetic diamonds is mainly composed of octahedral(111)plane and cubic(100)plane.The yield rate of the round bright cut diamonds is between 20%and 67%.The clarity grades of colorless HPHT synthetic diamonds range from VVS to P,and color grades are between D to H.GV5000 is employed to perform a study of both growth structure and luminescence characteristics of the samples.The cubic-octahedral luminescence patterns related to crystal growth structure can be observed in all samples of three colors.The colorless samples show strong blue fluorescence and phosphorescence.The luminescence peak is at 495 nm,which is related to the paramagnetic nitrogen in the lattice.The blue samples show blue to greenish blue fluorescence and blue phosphorescence,with the luminescence peak at 501 nm,related to the paramagnetic nitrogen and boron in the lattice.The yellow samples show weak green fluorescence and phosphorescence and the luminescence peaks related to Ni^+are at 556 and 883 nm.Synthetic diamonds with those features above can be distinguished from natural ones.Infrared absorption spectra show that the colorless HPHT synthetic diamonds having no significant nitrogen-related absorption at 1 332~1 100 cm^-1,with boron(B^0)related absorption at 2 802 cm^-1,are classified as typeⅡa containing a small amount of boron.The blue HPHT synthetic diamonds are typeⅡb with strong boron-related absorption at 1 294 cm^-1.The yellow HPHT synthetic diamond samples are typeⅠb with obvious absorption peaks at 1 130 and 1 344 cm^-1 which are caused by single nitrogen.Luminescence peaks related to Ni defects at 659,694,708,714 and 883 nm are observed in colorless,blue and yellow samples under photoluminescence spectra(PL5000).In contrast,natural colorless and yellow diamonds are usually typeⅠa,with infrared absorption peaks at 1 282 and 1 175 cm^-1 caused by aggregate nitrogen.Zero phonon lines at 415 nm(N3)can be detected by photoluminescence spectra.Spectral features caused by isolated nitrogen,boron and nickel are extremely rare in natural colorless and yellow diamonds.Therefore,infrared absorption spectra and photoluminescence spectra features can be used as the significant evidence for identification.The main composition of the extrusive inclusions in colorless HPHT synthetic diamonds turns out to be Fe by LIBS.EDS analysis displays that among samples with a relatively large number of inclusions,Fe is detected in blue and colorless samples,and Fe and Ni are tested in yellow samples.Both Fe and Ni are compositions of inclusions,which can be used as one of the identifiable characteristics of HPHT synthetic diamonds.In conclusion,the large grained HPHT synthetic diamonds can be distinguished from natural diamonds based on the fluorescence and phosphorescence characteristics under ultra-short ultraviolet light irradiation(GV5000),accompanied by infrared absorption spectra,photoluminescence spectra(PL5000)and X-ray energy dispersive analysis features.