Influence of Boron Content in Diamond on Color and Thermal Stability of Synthetic Diamond

In order to investigate the influence of boron content in the diamond on the color and thermal stability of diamond,boron-doped diamond was synthesized under high pressure and high temperature,using graphite and alloy catalyst powders as starting materials,and boric acid as addictives.The boron contents in the diamond crystals were quantitatively measured by the atomic-emitting spectrum method.Further,thermogravimetric analysis(TGA) and differential scanning calorimetry(DSC) in flowing air were used to analyze thermal stability of synthetic diamond.The colors of synthetic diamond crystals were observed with the help of a stereomicroscope.The results indicate that the synthesized diamond has the initial oxygenation temperatures of over 840 ℃,even up to 920 ℃,and the exothermic summit of approximate 990 ℃,even up to 1135 ℃,and the weight loss from 58% to 94% at 1200 ℃.With the increase of the boron content,the color of the diamond turns from yellow to dark,the thermal stability of diamond gets better.Transparent yellow diamond with good thermal stability can be obtained if the contents of boron element in the diamond are controlled below 30 ppm.