Dependence of Crystal Quality and β Value on Synthesis Temperature in Growing Gem Diamond Crystals

High quality Ib gem diamond single crystals were synthesized in cubic anvil high-pressure apparatus （SPD- 6 × 1200） under 5.4GPa and 1230℃-1280℃. The （100） face of seed crystal was used as growth face, and Ni70Mn25Co5 alloy was used as solvent/catalyst. The dependence of crystal quality andβ value （the ratio of height to diameter of diamond crystal） on synthesis temperature was studied. When the synthesis temperature is between 1230℃ and 1280℃, theβ value of the synthetic high-quality gem diamond crystals is between 0.4 and 0.6. The results show that when theβ value is between 0.4 and O. 45, the synthetic diamonds are sheet-shape crystals; however, when theβ value is between 0.45 and 0.6, the synthetic diamonds are tower-shape crystals. In addition, when theβ value is less than 0.4, skeleton crystals will appear. When theβ value is more than 0.6, most of the synthetic diamond crystals are inferior crystals.     

快速合成立方六面体金刚石大单晶晶体的质量研究

利用高温高压温度梯度法,在优质六面体金刚石大单晶稳定生长的基础上,合理调整晶床高度为5 rmm,在1300～1350℃温度区域30h合成优质六面体晶体重量达2.04克拉,生长速度高达13.6 mg/h.三种晶体样品(本实验合成晶体,日本住友公司合成晶体,元素六公司合成晶体)经显微红外吸收(IR)测试,本实验合成晶体{100}晶面的平均氮含量为240 ppm,高于日本住友和元素六晶体样品的氮含量;三种晶体样品经激光拉曼测试,均在1332 cm-1左右出现了较强的金刚石拉曼标准峰,利用高斯模拟计算出本实验合成晶体拉曼峰的半高宽值为5.570cm-1,大于日本住友晶体样品而小于元素六合成的晶体样品;对三种晶体样品的生长速度、氮含量分布和晶格结晶程度分析,由于本实验合成六面体晶体的生长速度远大于二者,使晶体的晶格结晶程度稍差于日本住友样品而优于元素六晶体,结合激光拉曼图谱分析本实验合成的六面体晶体中有少量杂质存在,或许这些杂质的存在正是导致其{100}晶面氮含量高于日本住友样品氮含量的主要原因.     

高温高压生长宝石级金刚石单晶的表面特征研究

本文利用高温高压温度梯度法,NiMnCo合金作为触媒,分别采用籽晶{100}和{111}作为生长面,合成了Ib型宝石级金刚石单晶,对其表面特征进行了分析和讨论.结果发现,宝石级金刚石单晶的表面特征不具有唯一性,多数情况下,晶体{111}面明显较{100}面平整,而且{100}面生长台阶的棱角不清晰,经常会出现经触媒融融过的痕迹,并且这种现象的出现跟籽晶生长面不同和合成温度条件高低无关;{111}面有时也会出现明显的生长台阶,棱角清晰,并且形状较为规则.宝石级金刚石晶体表面特征的不唯一性说明晶体表面特征对生长条件稳定性有更高的要求.     

在NiMnCo-Cu-C体系中生长宝石级金刚石单晶

利用温度梯度法在NiMnCo-Cu-C体系、于5.5 GPa、1250℃条件下进行了宝石级金刚石单晶的生长研究,结果发现,Cu片在触媒中的放置位置和其在金属触媒中所占体积分数对宝石级金刚石单晶的生长具有明显影响.当Cu片放置在碳源和触媒之间时,将不会有充足的碳源扩散到籽晶上,晶体无法生长;但放在触媒中其他位置,体积分数适当时,不会对晶体生长有明显影响.随着Cu体积分数增加,优质晶体生长将变得困难,当体积分数在20;时,晶体有生长,但晶体内部跟表面明显存在由于包裹体存在造成的生长坑洞;当体积分数在40;左右时,晶体将不再生长.不过当Cu在触媒中的体积分数适当时,会降低碳源在触媒中的输运,从而对抑制自发核生长起到一定的作用.     

HPHT Synthesis of Different Shape Coarse-Grain Diamond Single Crystals

Synthesis of coarse-grain diamond crystals is studied in a China-type SPD6× 1670T cubic high-pressure apparatus with high exact control system. To synthesize high quality coarse-grain diamond crystals, advanced indirect heat assembly, powder catalyst technology and optimized synthesis craft are used. At last, three kinds of coarse- grain diamond （about 0.85 mm） single crystals with hexahedron, hex-octahedron and octahedron are synthesized successfully under HPHT （about 5.4 GPa, 1300-1450℃）. The growth characters of different shape crystals are discussed. The results and techniques might be useful for the production of coarse-grain diamonds.     

HPHT Synthesis of Micron Grade Boron-Doped Diamond Single Crystal in Fe-Ni-C-B Systems

Micron grade boron-doped diamond crystals with octahedral morphology are successfully synthesized in a Fe-Ni- C-B system under high pressure and high temperature （HPHT）. The effects of the additive boron on synthesis conditions, nucleation and growth, crystal morphology of diamond are studied. The synthesized micron grade diamond crystals were characterized by optical microscope （OM）, scanning electron microscope （SEM）, x-ray diffraction （XRD） and Raman spectroscopy. The research results show that the V-shaped section of synthetic diamond moves downwards to the utmost extent due to 0.3a wt% （a is a constant.） boron added in the synthesis system. The crystal colour is black, and the average crystal size is about 25μm. The crystal faces of synthetic diamond are mainly （111） face. The synthesis of this kind of diamond is few reported, and it will have important and widely applications.     

天然和培育金刚石品质表征与呈色分析

金刚石是集最高硬度、超宽禁带、最高热导率等优异性能于一体的典型超硬多功能材料，天然金刚石储量低且价格昂贵，其中彩色天然金刚石在自然界中产储量极其稀少且致色机制较为复杂。高温高压法是制备金刚石的有效手段，然而调控金刚石颜色获得可控的彩色金刚石，仍面临极大挑战。本文通过对粉色、绿色天然和高温高压温度梯度法制备的金刚石进行一系列拉曼、荧光、红外和可见光吸收测试，详细地研究其品质、缺陷随温度变化及致色原因，发现彩色金刚石致色与电中性的N₂V缺陷(H₃)、剪切应力、塑性形变和NV⁰/NV^-色心等因素相关。通过各种手段获得不同颜色的金刚石不仅是为了其欣赏及收藏价值，其颜色的调控也有助于人们对金刚石形成机制的进一步了解，为培育彩色金刚石提供新的参考。     

Effects of Al and Ti/Cu on Synthesis of Type-IIa Diamond Crystals in Ni70Mn25Co5-C System at HPHT

High-quality type-Ⅱa gem diamond crystals are successfully synthesized in a NiToMn25Co5-C system by temperature gradient method （TGM） at about 5.5 GPa and 1560 K. Al and Ti/Cu are used as nitrogen getters respectively. While nitrogen getter Al or Ti/Cu is added into the synthesis system, some inclusions and caves tend to be introduced into the crystals. When Al is added into the solvent alloy, we would hardly gain high-quality type-Ⅱa diamond crystals with nitrogen concentration Nc 〈 1 ppm because of the reversible reaction of Al and N at high pressure and high temperature （HPHT）. Piowever, when Ti/Cu is added into the solvent alloy, high-quality type-Ⅱa diamond crystals with Nc 〈 1 ppm can be grown by decreasing the growth rate of diamonds.     

多余碳源的析出形式与宝石级金刚石单晶生长

温度梯度法生长宝石级金刚石单晶过程中,当籽晶无法完全吸收由高温端扩散下来的碳源时,多余碳源的不同析出形式(再结晶石墨或者自发核)对晶体生长速度有明显的影响。当大量多余碳源以再结晶石墨形式析出时,和以金刚石自发核形式析出不同,晶体的生长速度受到较为明显的抑制作用。例如,以NiMnCo触媒为例,随着合成温度的提高,当多余碳源不再以金刚石自发核形式析出,而是以大量片状再结晶石墨形式围绕在晶体周围时,晶体的生长速度从相对低温时的约3.0mg/h降到较高温度时的1.0mg/h;此外,随着合成压力由5.5GPa降到5.2GPa,晶体生长速度由3.0mg/h降到1.0mg/h,多余碳源析出形式也由金刚石自发核变化为再结晶石墨。     

用不同粒度的籽晶生长优质宝石级金刚石单晶

利用温度梯度法生长宝石级金刚石单晶过程中,由于籽晶接收碳源能力有限,单一晶种将很难完全吸收扩散下来的碳源,因而导致籽晶的粒度对晶体生长速度和品质都会产生很大影响.随着籽晶粒度的增大,晶体的生长速度增幅非常明显,但不是粒度越大越好,存在临界粒度,超过临界粒度,优质单晶就很难生长.以NiMnCo触媒为例,籽晶粒度由0.5mm增加到2.0mm后,晶体的生长速度可由1.0mg/h提高到3.0mg/h,但籽晶粒度超过2mm后,晶体内部包裹体大幅度增加.