在Fe-Al-C系统中合成优质IIa型宝石级金刚石单晶

和优质Ib型宝石级金刚石单晶生长相比,作为当今高温高压晶体生长的一种高精尖技术,优质Ⅱa型宝石级金刚石单晶对合成技术提出了更高更苛刻的要求。本研究从晶体的生长速度出发,发现一开始阶段(大约几个小时)的晶体生长速度对优质宝石级金刚石单晶的后期生长至关重要。对Fe-A l-C系统(A l含量不大于2.5wt%)来说,采用多晶种法将晶体开始阶段的晶体生长速度由1.5mg/h降至0.5mg/h后,对生长过程中金属包裹体的进入有了明显的抑制作用,晶体的质量有了很大提高。从晶体中包裹体的存在形式来看,为了获得优质Ⅱa型宝石级金刚石单晶,在触媒中人为地添加除氮剂给晶体生长过程中的排杂过程带来了很大的难度。为了更好的实现排杂,必须很好的处理晶体表面的径向平铺生长速度和晶体轴向的堆积生长速度之间的关系。

Growth of high-quality type IIa gem diamonds in Fe-Al-C system

Compared with the growth of type Ib gem diamonds by temperature gradient method,a more demanding synthetic(technique) is necessary to grow high-quality type IIa gem crystals.In this paper,synthesising experiment of type IIa gem diamond was conducted in Fe-Al-C system.It is found that the growth rate in the first growing hours is of great importance to the quality of the grown crystal.When the growth rate decreases from 1.5mg/h to 0.5mg/h with multi-seed growth method,it turns more difficult for the metal inclusions to be incorporated into the grown crystals,and the crystal quality is greatly improved.From the present forms of metal inclusions in the crystals,it can be found that the impurity-removing process becomes more difficult,because of the artificial addition of nitrogen-getters into the metal catalyst.So as to grow high-quality type IIa gem diamonds,it is necessary to control the correlations between the radical growth rate and the axial growth rate.