Application And Research Of The Ion Implantation On Gemstone Surface Color Improvement

In this study, experiments were conducted to explore the application of ionimplantation technique on surface of gemstone. The gemological features andexistence forms of implanted ions were analyzed. Combined with some othertechniques to improve the color of gemstone, the identical features were concluded,according to the respective characteristics of the samples studied.In order to improve the color of particular part on surface of gemstone,implantation conditions, such as accelerating voltage, beam intensity implantationdose, and annealing conditions, including the heating rate, upper limit temperatureand temperature constance, should be strictly controlled in the ion implantationtechniques. In this experiment conducted, beryl, jadeite and marble have shownrelatively better color improvement. Poor color improvement may be attributed toless implantation dose and weak annealing oxidized environment.Samples with implanted ions have shown characteristics below:1. undermagnification, implantation layer did not cover the sample original structure and didnot show metallic luster as shown in the coated samples. The color distribution isrelatively even.2. Reflective index, density and hardness of the ion implantedsamples are the same to those sampled without ion implanted. Difference is that theformer do not show luminescence.3. The IR of samples implanted show the offset ofpeak to the low frequency or stronger peak in the low frequency. Mineral grains withuneven surface were observed under SEM.4.Concluded from the XPS analysis; theions implanted into the samples with high speed are normally Cr, which distortedwhen entering the crystal lattice and were partially oxidized during the implantation.Cr were oxidized and penetrated into the samples by annealing, thus, leading to ahigh concentration inside. In different base, the Cr ions are trivalent, which showsthat the Cr ions have entered the crystal lattice of the samples. The coloration is dueto the entrance of Cr3+and replacement of Al3+by Cr3+. Resulting from the low doseof implantation of Cr, some samples exhibit very light color or colorless.The difference between ion implantation technique and other color improvement methods (film, coating, diffusion) can be concluded as follows:1.Thefilm method is relatively easy to be performed on gemstone, gas bubbles may beseen under magnification and the coating layer may fall off as time goes by.2.Having developed for three generations, the coating method is mature so far, theproduct may have a variety of colors and metallic luster on the surface.3. In thediffusion product, color always concentrate on the fractures that reach to the surfaceand pits on the surface.4. Ion implantation technique can achieve color developmenton a particular part, but the color is comparatively light and the transparence is poor.Although it sill in research stage, ion implantation has a promising future in thegemstone and jewelry market, as a new technique of surface treating.