高温高压下Cu在Ⅱa型金刚石大单晶Ti除氮反应中的作用机理

The effect of adding Cu on the nitrogen removal efficiencyof Ti for the synthesis of a large type Ⅱa diamond under high temperature and high pressure

研究Cu在高温高压下Ti除氮反应中的作用机理,对合成优质的Ⅱa型金刚石晶体具有重要意义。本研究在FeNi-C体系中添加Ti和Ti/Cu或TiC和TiC/Cu,在5.6 GPa和1543 K的条件下使用温度梯度法制备了金刚石大单晶,并使用光学显微镜和红外光谱仪对样品进行表征。结果表明,Ti或TiC分别与N反应生成TiN和Ti(C1-x,Nx)。这种情况下,单独添加Ti或TiC除氮效果差,所合成金刚石晶体中会出现大量的包裹体和凹坑。这是由于反应生成的TiN、TiC和Ti(C1-x,Nx)杂质严重影响晶体质量的结果。Ti或TiC分别与Cu共掺杂,可以促进TiC的分解释放Ti,提高除氮效率,并逐渐减少晶体合成中的缺陷和包裹体数量。这说明Cu的添加量应明显小于Ti,这与普通Ti和Cu的添加比例1∶1不同。最终结果表明,当Ti/Cu质量分数为1.70%/1.06%(Ti∶Cu=1∶0.625)时,可以合成出高质量的Ⅱa型金刚石晶体。

Large single crystal diamonds were synthesized using Ti/TiC and Cu as additives in the Fe 64 Ni 36-C system under 5.6 GPa and at 1543 K.The synthesized crystals were characterized by optical microscopy and infrared spectroscopy.Results show that both Ti and TiC react with N to form TiN and Ti(C1-x,Nx),respectively,which leads to a poor nitrogen removal efficiency and a large number of inclusions and pits in the crystals.Co-doping Ti or TiC with Cu promotes the decomposition of TiC to release Ti,which improves the nitrogen removal efficiency,and thereby reduces the number of defects and inclusions in the diamond crystals.A high-quality type Ⅱa diamond crystal was optimally synthesized when the Ti/Cu contents were 1.70 wt.%/1.06 wt.%(Ti:Cu=4:2.5).