Rare-earth metal catalysts for high-pressure synthesis of rare diamonds
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-04-19 |
| Journal | Scientific Reports |
| Authors | Yuri N. Palyanov, Yuri M. Borzdov, Igor N. Kupriyanov, Alexander F. Khohkhryakov, Denis V. Nechaev |
| Institutions | V.S. Sobolev Institute of Geology and Mineralogy |
| Citations | 9 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive Summaryâ- Novel Catalytic System: The study successfully established 15 Rare-Earth Metals (REM) as effective solvent-catalysts for High-Pressure High-Temperature (HPHT) diamond synthesis at 7.8 GPa and 1800-2100 °C.
- Nitrogen Gettering: All synthesized diamonds are confirmed to be nitrogen-free (Type II), demonstrating that REMs inherently function as highly effective nitrogen getters, eliminating the need for traditional getter additives (e.g., Ti, Zr).
- High Efficiency: Highly effective REMs (Sc, Ce, Tm, Lu) achieved graphite-to-diamond conversion rates up to 100% at 2000 °C, with maximum linear growth rates reaching 800 ”m/h (La-C system).
- Quantum Doping Success: The REM-C systems provide growth conditions favorable for the incorporation of Group IV elements (Si, Ge, Sn), leading to the formation of high-intensity Silicon-Vacancy (SiV-), Germanium-Vacancy (GeV-), and Tin-Vacancy (SnV-) color centers.
- Morphological Control: Diamond morphology is strongly dependent on the REM catalyst composition, ranging from simple octahedral habits (light REMs like La, Ce) to complex forms bound by tetragon-trioctahedron and trigon-trioctahedron faces (heavy REMs like Er, Lu).
- Type IIb Synthesis: Diamonds synthesized using heavy REMs (Tb-Lu) and Sc/Y frequently showed B-related absorption, corresponding to Type IIb semiconducting diamond, with boron concentrations estimated between 0.1 and 1 atomic ppm.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Synthesis Pressure | 7.8 | GPa | All experiments |
| Synthesis Temperature Range | 1800-2100 | °C | All experiments |
| Max Graphite-to-Diamond Conversion (a) | 100 | % | Sc-C system (2000 °C) |
| Max Linear Growth Rate (V) | 800 | ”m/h | La-C system (2000 °C) |
| Typical Nucleation Density (N) | 36 to 400 | cm-2 | Most REM systems (2000 °C) |
| Anomalous Nucleation Density (N) | 10,000 | cm-2 | Sm-C system (2000 °C) |
| Max Single Crystal Size | 2 | mm | Ce-C system |
| Diamond Type | II (Nitrogen-free) | N/A | All synthesized diamonds |
| Boron Concentration (Type IIb) | 0.1-1 | atomic ppm | Heavy REMs (Tb-Lu), Sc, Y catalysts |
| SiV- Zero-Phonon Line (ZPL) | 737 | nm | Dominant center in most samples |
| GeV- ZPL | 602 | nm | Achieved via Ge doping (Ce-Ge-C system) |
| SnV- ZPL | 620 | nm | Achieved via Sn doping (Ce-Sn-C system) |
| Starting Graphite Purity | 99.97 | % | Used for carbon source |
| Starting REM Purity | 99.99 | % | Used for solvent-catalyst |
Key Methodologies
Section titled âKey Methodologiesâ- Apparatus: Experiments were conducted using a split-sphere multi-anvil high-pressure apparatus.
- Pressure/Temperature Control: Pressure was maintained at 7.8 GPa. Temperature was varied between 1800 °C and 2100 °C. Run times were 1 hour for 1900-2100 °C runs, and 3-4 hours for 1800 °C runs.
- Starting Materials: Graphite rods (99.97% purity), Rare-Earth Metals (99.99% purity), and synthetic diamond seed crystals (0.5 mm cuboctahedrons) were used.
- Cell Assembly: Graphite rods were machined into thick-walled capsules (1.5 mm wall thickness). A piece of REM metal was placed in the center hole (3.9 mm diameter, 3.5 mm height), and four seed crystals were placed at the metal-graphite interface.
- Oxidation Prevention: Graphite capsules were enveloped with a 0.1 mm thick Molybdenum (Mo) foil to prevent penetration of high-pressure cell components. The assembled cells were dried in a vacuum oven at 100 °C for 24 hours, followed by argon filling.
- Doping Experiments: For Group IV doping, 10 wt% of Ge or Sn was added to the Ce-C and Ho-C systems.
- Post-Synthesis Processing: Products were recovered by dissolving the cell components in a hot mixture of nitric and hydrochloric acids. Residual graphite was removed from diamond surfaces using an aqueous solution of K2Cr2O7 and concentrated H2SO4.
- Characterization:
- Morphology: Optical microscopy, Scanning Electron Microscopy (SEM), and goniometric measurements.
- Surface Microrelief: Differential Interference Contrast (DIC) and Total Interference Contrast (TIC) methods were used to profile stepped combination surfaces.
- Impurity Analysis: Fourier Transform Infrared (FTIR) spectroscopy (for N and B content).
- Color Centers: Photoluminescence (PL) spectroscopy (excited at 395 nm, recorded at 80 K).
Commercial Applications
Section titled âCommercial Applicationsâ- Quantum Technologies: The ability to synthesize diamonds containing high concentrations of specific Group IV vacancy centers (SiV-, GeV-, SnV-) is critical for:
- Solid-State Quantum Computing: Utilizing the spin properties of these centers as qubits.
- Quantum Sensing and Metrology: Creating highly sensitive sensors based on diamond defects.
- Single-Photon Emitters: Developing stable, room-temperature light sources for quantum communication.
- High-Power Electronics and Optics: The production of large, high-quality, nitrogen-free (Type II) diamond crystals is essential for:
- Heat Sinks: Diamondâs superior thermal conductivity requires Type II material.
- High-Frequency/High-Power Devices: Utilizing Type IIb (boron-doped semiconducting) diamond synthesized efficiently using heavy REMs.
- Optical Windows: Creating robust, low-absorption optical components.
- Advanced Materials Research: The REM-C system provides a unique, ultra-reducing chemical environment, opening new pathways for synthesizing diamond doped with other elements or creating novel defect structures not achievable with traditional Fe-Ni-Co catalysts.
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
Section titled âReferencesâ- 1999 - Advances in New Diamond Science and Technology
- 1979 - The Properties of Diamond
- 1992 - The Properties of Natural and Synthetic Diamond
- 2015 - Handbook of Crystal Growth (Chap. 17) [Crossref]