High Pressure - High Temperature Treatment of Natural Diamonds
作者单位：Hoge Raad voor DiamantGDI Research Department c/o WTOCDPlaslaar 50B-2500LierBelgium Institute of Mineralogy and PetrographySiberian Branch of the Russian Academy of SciencesPr.Ac.Koptyuga 3630090 NovosibirskRussia
会议名称：《18th International Conference on High Pressure Science and Technology》
会议日期：2001年
学科分类：081702[工学-化学工艺] 08[工学] 0817[工学-化学工程与技术]
关 键 词：Natural Diamond HPHT treatment Colour Centers
摘 要：正 The results are reported of High Pressure - High Temperature （HPHT） treatment experiments for natural diamonds of different origin and with different impurity content. Diamonds are annealed in a temperature range up to 2100℃ at stabilizing pressures up to 70 000 atmospheres. The evolution is studied, as a function of temperature, pressure and time, of different impurities in the diamond crystal lattice. The most common impurities in diamond are subtitutional Nitrogen atoms. These can be present in isolated form, or in aggregates of two, three, four and more atoms, very often in combination with vacancies. According to the dominant Nitrogen aggregate impurity type, diamonds are classified in categories such as type laA, type laB, type laAB, type Ib and type Ha. It is found that the results of the HPHT treatment depend strongly on the diamond type. Moreover it turns out that the presence of additional impurities, mainly related to lattice distortion, can lead to totally different results. The diamonds are characterized using UV-Visible spectrophotometry, Fourier Transform Infrared （FTIR） spectrophotometry and photoluminescence spectrometry, at room temperature as well as at cryogenic temperature. Characteristic optical centers of known composition are studied, such as e.g. N3, H2, H3 and H4. Moreover the spectra show a number of peaks of which the nature is not known. High Pressure - High Temperature treatments of natural gem quality diamonds have become very important recently, because of the colour changes they can induce. These colour changes can lead to tremendous price differences. For the stability of the diamond trade it is very important to develop methods to make the distinction between natural and treated colours. In several cases this distinction can not be made at present. Therefore a systematic study of the influence of HPHT treatment on different diamond types is most necessary.