| Jadeite jade is a kind of pyroxene mineral aggregate, and its main composition is NaAlSi2O6. Due to the lack of natural jade resources, the price is high, and therefore people focus on the synthetic jadeite. In the 1980s, some scientific research institutions in China have carried on the synthetic test of jadeite, such as Jilin University, Chinese academy of sciences applied chemistry and Guiyang's academy of sciences, but the synthetic effect is not ideal. Their products often contain a lot of vitreous composition of jade or a mixture of small crystal powder.In 2002, GIA first published reports on the gem-quality synthetic jade. GE's synthetic samples are green color, good transparency and reaching a gem-quality standard, but there is a certain difference from natural jade. We rarely know public information about the gem-quality synthetic emerald, and thus the research about this is basically in a blank state. It can be said that the research of GE has made great achievement, but the domestic research obtained little progress in this field.In our laboratory, we develop the new research to synthesize jadeite on the basis of adding the color-causing elements Mn and Cr. We work on the research of the mechanism of synthesis and the analysis of result around the jade. Our work is divided into the following four sections:Firstly, the mixture of high purity Al2(Si03)3 (99.99%) and Na2Si03 (99.99%) powders with a molar ratio of 1:1 are used as raw materials, which is toasted grinding and quenching moulding made from glass material. We analyze the composition of the glass by means of XRD. The composition is complicated, and which generally can be divided into two categories:one is the breakdown products of raw materials, and the other one is synthetic compounds of the raw materials.Secondly, the best temperature of synthetic jadeite increases with the pressure rise. Under the pressure of 4.0,4.5,5.0 and 5.5 GPa, the optimum temperature are 1300,1370,1450 and 1500 ?. respectively. The color of milky white and degree of water embellish of synthetic jadeite under the pressure of 5.0 and 5.5 GPa are better than that of 4.0 and 4.5 GPa. Through the XRD patterns, FTIR and SEM images, we found that the main component of the synthetic samples is NaAlSi2Oe, and the samples possess the fibers woven structure of column with granular.Thirdly, we mixed a small amount of MnO into the synthetic jadeite, and carried out the exploring experiment under the best synthetic conditions of jadeite. The colors of the synthetic samples mainly present pink/purple and light purple. The results are mainly decided by the concentration of MnO, and the higher the concentration, the deeper the color. We analyze result of XPS test and consider that Al and Mn ions do not bond alternately, and the Mn ions exist in interstitial void. The color-causing mechanism is similar to the theory of the lattice imperfection.Finally, the raw materials are mixed with.Cr2O3 from 0.2% wt. to 1% wt, and the synthetic conditions are the same as above. We found that with the concentration increasing, the color of the synthetic samples is change from bright green to emerald green and dark green finally. After compared with natural jade, the main components of the synthetic samples are same as the former, and both possess the similar fiber woven structure and molecular structure. The XPS test was carried out on the synthetic and natural jadeite jade. We assume that Al and Cr ions bond alternately, and color-causing mechanism is caused by the charge migration among the ions. |
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