Abstract
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.
Highlights
The investigation of the optical properties of rare-earth (RE) ions in various crystalline matrices has attracted the interest of many researchers
This is most clearly seen in the case of significant diamond growth that occurred in the europium oxalate melt (Figure 1a)
Diamond growth on seed the high temperatures, applied in the synthesis experiments, the seed diamond crystals had undergone crystals was realized all experiments at 2000 °C.ofThe highestofgrowth rate occurred in the europium an annealing processinresulting in the formation a variety
Summary
The investigation of the optical properties of rare-earth (RE) ions in various crystalline matrices has attracted the interest of many researchers. Rare-earth ions have unique optical properties, in particular narrow-band luminescence, with a long decay time and an exceptionally long nuclear spin coherence time [1,2]. The technological interest in rare-earth luminescence is quite wide and includes telecommunications, laser materials, data storage, bio-medical applications and many other fields of application. In this regard, of considerable interest is the search for new systems for diamond growth, which will involve the doping of diamonds with RE ions. The problem of producing diamond crystals doped with rare-earth elements remains unresolved
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