坦桑石的矿物学及谱学特征研究
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摘要
对来自坦桑尼亚Merelani地区的坦桑石样品,分别采用电子探针、EMXPLUS型ESR谱仪、同步热分析仪、紫外可见光谱仪以及傅里叶变换红外光谱仪进行了测试与分析。结果表明:坦桑石样品的主要成分为SiO_2,Al_2O_3和CaO,微量成分中V_2O_5含量相对最多,平均含量为0.36%;坦桑石样品本身不含吸附水,结晶水,加热至780℃附近时,脱失结构水,样品中结构水大约占总质量的2%;ESR实验结果中显示出明显Fe~(3+)和Mn~(2+)的电子顺磁信号;紫外-可见光谱显示,样品在385nm处出现吸收窄带,575和750nm处分别出现较为宽缓的吸收;红外光谱测试表明,样品在6 500~9 000cm~(-1)波段的倍频振动区,基本没有吸收。在4 000~6 500cm~(-1)波段主要为和频振动,5 956cm~(-1)附近呈较宽缓的吸收峰,5 413,5 184,4 336和4 046cm~(-1)处出现较尖锐的吸收峰,主要可能由O—H,矿物内的Si—O,以及空气里面的H_2O分子和CO_2振动所引起。综合EPMA以及ESR分析结果,蓝-紫色坦桑石颜色可能主要由V~(3+)和V~(5+)共同引起,Fe~(3+)晶体场的d—d电子跃迁、Fe~(2+)→Ti~(4+)的电荷转移辅助致色。
In this paper,the Tanzanite samples from Merelani Tanzania have been respectively tested and analyzed by electron probe,EMXPLUS ESR spectrometer;SDT,UV VIS spectrometer and Fu Liye transform infrared spectrometer.The results show that:the Tanzanite samples are mainly composed of SiO_2,Al_2O_3and CaO,V_2O_5has the content of 0.36%,which is the most trace components;TG-DTA curves show that there is no absorption water and crystal water in Tanzanite samples,when being heated to 780℃,the structural water is lost,the water in the samples is about 2%of the total mass;ESR results shows obvious Fe~(3+)and Mn~(2+)electron paramagnetic signal;UV Vis spectra shows that an narrow-band absorption appears at 385nm while a wide-band absorption appears respectively at 575and 750nm;infrared spectra shows that there is no absorption in 6 500~9 000cm~(-1) of the Tanzanite samples.The 5 956cm~(-1)is a wide absorption peak,and there is a sharp absorption peak respectively at 5 413,5 184,4 336,and 4 046cm~(-1),which are mainly caused by the O—H,the Si—O within in the minerals as well as H_2O and CO_2inside the air environment.Based on the results of EPMA and ESR analysis,the color of blue-violet Tanzanite may be mainly caused by V~(3+)and V~(5+),d—delectron transition of the crystal field of Fe~(3+)and charge transfer of Fe~(2+)to Ti ~(4+)to assist coloration.
In this paper,the Tanzanite samples from Merelani Tanzania have been respectively tested and analyzed by electron probe,EMXPLUS ESR spectrometer;SDT,UV VIS spectrometer and Fu Liye transform infrared spectrometer.The results show that:the Tanzanite samples are mainly composed of SiO_2,Al_2O_3and CaO,V_2O_5has the content of 0.36%,which is the most trace components;TG-DTA curves show that there is no absorption water and crystal water in Tanzanite samples,when being heated to 780℃,the structural water is lost,the water in the samples is about 2%of the total mass;ESR results shows obvious Fe~(3+)and Mn~(2+)electron paramagnetic signal;UV Vis spectra shows that an narrow-band absorption appears at 385nm while a wide-band absorption appears respectively at 575and 750nm;infrared spectra shows that there is no absorption in 6 500~9 000cm~(-1) of the Tanzanite samples.The 5 956cm~(-1)is a wide absorption peak,and there is a sharp absorption peak respectively at 5 413,5 184,4 336,and 4 046cm~(-1),which are mainly caused by the O—H,the Si—O within in the minerals as well as H_2O and CO_2inside the air environment.Based on the results of EPMA and ESR analysis,the color of blue-violet Tanzanite may be mainly caused by V~(3+)and V~(5+),d—delectron transition of the crystal field of Fe~(3+)and charge transfer of Fe~(2+)to Ti ~(4+)to assist coloration.
引文
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[4]Bernard Olivier.The Geology and Petrology of the Merelani Tanzanite Deposit,NE Tanzania.
[5]deBiasi R S,Fernandes A A R.Communications of the American Ceramic Society,September,1984,C-173.
[6]QI Li-jian,YE Song,XIANG Chang-jin(亓利剑,叶松,向长金).Journal of Earth Science(地球科学),1998,(1):32.
[7]LIU Hong-ke,DU Hong-mei,KU Yu-miao,et al(刘宏科,杜红梅,库育苗,等).Guangdong Chemical Industry(广东化工),2014,(16):172.
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