Application of Infrared Spectroscopy and Raman Spectroscopy on Identification of Heat-treated Aquamarine
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摘要: 在适当的热处理条件下，黄绿色绿柱石能够转变为理想颜色的海蓝宝石。天然海蓝宝石与热处理海蓝宝石的价格差异较大，因此探索热处理海蓝宝石的诊断性鉴定特征就显得十分必要。对不同温度下热处理海蓝宝石进行傅里叶变换红外光谱和激光拉曼光谱的测试分析，结果发现，当热处理温度超过400℃后，随着加热温度的升高，在红外光谱中由［Fe2（OH）4］2＋伸缩振动引起的3 233cm-1处吸收谱峰明显减弱，直至消失。5 268cm-1附近由水伸缩和弯曲振动引起合频区的吸收带由尖峰变得宽缓；8 700，6 818cm-1两处水吸收峰的相对强度也随着加热温度升高而减弱。热处理海蓝宝石Si－O－Si伸缩振动产生的在682，3 604cm-1处的拉曼光谱谱峰强度随着加热温度升高逐渐减弱，1 070cm-1处的拉曼峰强度明显降低。经700℃加热后，拉曼光谱基线明显向上方漂移。这些光谱特征变化对热处理海蓝宝石的鉴定有重要意义。Abstract: Experiments show that yellow-green beryls can be transformed into aquamarines by using appropriate heat treatment.However,in jewelry market,the price of natural aquamarine is quite different from that of heat-treated aquamarine.Thus exploring diagnostic identification characteristics of heat-treated aquamarine is of great importance.Previous identifications of heat-treated aquamarine were their internal inclusion characteristics,which were observed through microscope.However,it was difficult to identify flawless aquamarines.The authors selected some samples from Altay to treat under a reducing atmosphere at different temperatures for 3hours.Fourier transform infrared spectrometer and Raman spectroscopy were used to explore the characteristic absorption peaks of the heat-treated samples.The results show when the heating temperature is above 400℃,the peak caused by the stretching vibration of[Fe2(OH)4]2+ at 3 233cm-1 is significantly reduced or even disappeared and the sharp absorption peak around 5 268cm-1 caused by H2O becomes wide and gentle.The relative intensity of absorption peak at 8 700and 6 818cm-1 caused by H2O weakens as the heating temperature is elevated.It is found that the Raman spectral intensity at 682and 3 604cm-1caused by stretching vibration of Si-O-Si reduce as the heating temperature rises,and spectral intensity at 1 070cm-1 decreases.After heat treatment at 700℃,the baseline of Raman spectrum drifts upward obviously.
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Keywords:
- infrared spectrum /
- Raman spectrum /
- heat treatment /
- aquamarine
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