Effect of Rare-Earth Element Oxides on Diamond Crystallization in Mg-Based Systems

Crystals

AlexanderF. Khokhryakov¹  YuriN. Palyanov¹  YuriM. Borzdov¹  IgorN. Kupriyanov¹ 

[1] Sobolev Institute of Geology and Mineralogy SB RAS, Koptyug ave. 3, 630090 Novosibirsk, Russia;

关键词: diamond;    high-pressure;    high-temperature;    crystallization;    crystal morphology;    rare-earth ions;    defects;    characterization;   

DOI  :  10.3390/cryst9060300

来源: DOAJ

【 摘 要 】

Diamond crystallization in Mg-R₂O₃-C systems (R = Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb) was studied at 7.8 GPa and 1800 °C. It was found that rare-earth oxide additives in an amount of 10 wt % did not significantly affect both the degree of graphite-to-diamond conversion and crystal morphology relative to the Mg-C system. The effect of higher amounts of rare-earth oxide additives on diamond crystallization was studied for a Mg-Sm₂O₃-C system with a Sm₂O₃ content varied from 0 to 50 wt %. It was established that with an increase in the Sm₂O₃ content in the growth system, the degree of graphite-to-diamond conversion decreased from 80% at 10% Sm₂O₃ to 0% at 40% Sm₂O₃. At high Sm₂O₃ contents (40 and 50 wt %), instead of diamond, mass crystallization of metastable graphite was established. The observed changes in the degree of the graphite-to-diamond conversion, the changeover of diamond crystallization to the crystallization of metastable graphite, and the changes in diamond crystal morphology with increasing the Sm₂O₃ content attested the inhibiting effect of rare-earth oxides on diamond crystallization processes in the Mg-Sm-O-C system. The crystallized diamonds were studied by a suite of optical spectroscopy techniques, and the major characteristics of their defect and impurity structures were revealed. For diamond crystals produced with 10 wt % and 20 wt % Sm₂O₃ additives, a specific photoluminescence signal comprising four groups of lines centered at approximately 580, 620, 670, and 725 nm was detected, which was tentatively assigned to emission characteristic of Sm³⁺ ions.

【 授权许可】

Unknown