hBN-LiH/hBN-Li_3N-B体系合成cBN的赋色过程研究

在高温高压条件下,用hBN-LiH和hBN-Li3N-B为初始材料均可以合成出黑色cBN晶体。拉曼光谱测试结果表明,cBN晶体颜色变黑的原因是晶体中多余B原子的存在造成的。在hBN-Li3N-B体系中,晶体内部有明显的三角形阴影形成,表明从晶体表面的中心到顶角间B原子的含量较多,从表面中心到棱边B原子的含量逐渐减少。而在hBN-LiH体系中所得到的晶体颜色从黑色透明直接变成黑色不透明状态,晶体内部没有出现三角形阴影,表明晶体中作为杂质的B原子分布比较均匀。此两种情况说明,B作为杂质原子进入cBN晶体中可以有两种分布情况,一是居中对称分布,二是均匀分布,从晶体的生长环境和自身的排杂能力方面分析了晶体为什么会出现上述现象。

The Coloration Process Study on the Synthesis of cBN by hBN-LiH/hBN-Li3N-B System

Using hBN-LiH or hBN-Li₃N-B as starting materials, we synthesied black cBN crystals under high pressure and high temperature. The results of Raman spectrum show that the reason why cBN crystals become black is that the redundant B atoms get into them. The cBN crystal is synthesized in hBN-Li₃N-B system, and then we observe a trigonal shadow is formed clearly. This phenomenon indicates that there are more B atoms from center to apex in cBN crystal, and the B atoms content gradually decrease from center to edge. However, the color of cBN crystal which is synthesized in hBN-LiH system was from transparent black to opaque black directly, and the trigonal shadow does not be formed. This phenomenon indicates that the B atoms as impurity diffuse equably in cBN crystals. The two circumstances illustrate that as an impurity atom, B has two kinds of distributions when it enter into cBN crystal: one is centeral symmetric distribution, the other is uniform distribution. In this paper, we analyze the reason why cBN crystals have different phenomenon above according to its growth environment and its ability of excluding impurity.