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Open AccessArticle

Crystallization of Diamond from Melts of Europium Salts

1
Sobolev Institute of Geology and Mineralogy SB RAS, Koptyug ave. 3, 630090 Novosibirsk, Russia
2
Department of Geology and Geophysics, Novosibirsk State University, 630090 Novosibirsk, Russia
*
Author to whom correspondence should be addressed.
Crystals 2020, 10(5), 376; https://doi.org/10.3390/cryst10050376
Received: 17 April 2020 / Revised: 30 April 2020 / Accepted: 6 May 2020 / Published: 7 May 2020
(This article belongs to the Special Issue Diamond Crystals Volume II)
Diamond crystallization in melts of europium salts (Eu2(C2O4)3·10H2O, Eu2(CO3)3·3H2O, EuCl3, EuF3, EuF2) at 7.8 GPa and in a temperature range of 1800–2000 °C was studied for the first time. Diamond growth on seed crystals was realized at a temperature of 2000 °C. Spontaneous diamond nucleation at these parameters was observed only in an Eu oxalate melt. The maximum growth rate in the europium oxalate melt was 22.5 μm/h on the {100} faces and 12.5 μm/h on the {111} faces. The diamond formation intensity in the tested systems was found to decrease in the following sequence: Eu2(C2O4)3·10H2O > Eu2(CO3)3·3H2O > EuF3 > EuF2 = EuCl3. Diamond crystallization occurred in the region of stable octahedral growth in melts of Eu3+ salts and in the region of cubo-octahedral growth in an EuF2 melt. The microrelief of faces was characterized by specific features, depending on the system composition and diamond growth rate. In parallel with diamond growth, the formation of metastable graphite in the form of independent crystals and inclusions in diamond was observed. From the spectroscopic characterization, it was found that diamonds synthesized from Eu oxalate contain relatively high concentrations of nitrogen (about 1000−1200 ppm) and show weak PL features due to inclusions of Eu-containing species. View Full-Text
Keywords: diamond; high-pressure; high temperature; crystallization; crystal morphology; rare-earth ions; defects; characterization diamond; high-pressure; high temperature; crystallization; crystal morphology; rare-earth ions; defects; characterization
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Borzdov, Y.M.; Khokhryakov, A.F.; Kupriyanov, I.N.; Nechaev, D.V.; Palyanov, Y.N. Crystallization of Diamond from Melts of Europium Salts. Crystals 2020, 10, 376.

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