High-Pressure Synthesis of Superconducting Sn3S4 Using a Diamond Anvil Cell with a Boron-Doped Diamond Heater
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2022-02-28 |
| Journal | Inorganic Chemistry |
| Authors | Ryo Matsumoto, Kensei Terashima, Satoshi Nakano, Kazuki Nakamura, Sayaka Yamamoto |
| Institutions | Ehime University, National Institute for Materials Science |
| Citations | 9 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research details the successful high-pressure synthesis and characterization of the theoretically predicted cubic tin sulfide superconductor, Sn3S4, utilizing a specialized Diamond Anvil Cell (DAC).
- Enabling Technology: A highly robust DAC system was developed, integrating a Boron-Doped Diamond (BDD) heater, thermometer, and transport measurement terminals onto a culet-type diamond anvil, allowing for synthesis and in situ measurement above 30 GPa.
- Superconductivity Observed: The synthesized cubic Sn3S4 exhibits metallic behavior and superconductivity, reaching a maximum onset transition temperature (Tconset) of 13.3 K at 5.6 GPa.
- Phase Stability: The cubic Sn3S4 phase is synthesized above 25 GPa and remains stable during decompression within the pressure range P > 5 GPa, decomposing below 3.1 GPa.
- Pressure Dependence: Tc increases significantly as pressure decreases (positive pressure effect), which is consistent with first-principles calculations showing an enhancement of the electron-phonon coupling constant (λ) upon decompression.
- Structural Confirmation: In situ X-ray diffraction (XRD) and Raman spectroscopy confirmed the formation of the cubic Sn3S4 (I-43d) phase and its structural stability under pressure.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Maximum Tc (Onset) | 13.3 | K | Observed at 5.6 GPa during decompression |
| Maximum Tc (Zero Resistivity) | 8.5 | K | Observed at 5.6 GPa during decompression |
| Synthesis Pressure Range | > 33.4 | GPa | Initial compression for high-temperature synthesis |
| Synthesis Temperature | ~800 | K | Achieved using BDD heater |
| BDD Heater Input Power | ~19 | W | Power required to reach 800 K |
| Sn3S4 Stability Range | 6.2 < P < 41.1 | GPa | Confirmed by XRD and Raman spectroscopy |
| Decomposition Pressure | < 3.1 | GPa | Pressure at which Sn3S4 decomposes |
| Upper Critical Field (Bc2(0)) | 10.4 | T | Estimated at 5.6 GPa (parabolic fitting) |
| Coherence Length (Ο(0)) | 5.9 | nm | Estimated at 5.6 GPa using Ginzburg-Landau formula |
| Bulk Modulus (B0) | 97(6) | GPa | Fitted using Birch-Murnaghan equation of state |
| BDD Electrode Boron Conc. | > 1021 | cm-3 | Required for metallic conductivity |
| XRD X-ray Energy | 30 | keV | Synchrotron source (λ = 0.4180 A) |
| Raman Laser Wavelength | 532 | nm | Used for vibrational mode analysis |
Key Methodologies
Section titled âKey MethodologiesâThe synthesis and characterization relied on a highly specialized, integrated high-pressure system:
- DAC Modification: The standard DAC was improved by replacing the box-type anvil with a culet-type anvil and using a ZrO2 backup plate, enabling operation at pressures exceeding 30 GPa.
- BDD Component Fabrication: Boron-doped diamond (BDD) epitaxial films were fabricated onto the culet-type diamond anvil via Microwave Plasma-Assisted Chemical Vapor Deposition (MPCVD). These films were patterned using electron beam lithography to create integrated metallic measurement terminals, a metallic heater, and a semiconducting thermometer.
- Sample Loading: A well-ground stoichiometric mixture of SnS and SnS2 was loaded onto the BDD terminals within a gasket hole (200 ”m diameter). Cubic boron nitride (cBN) was used as the pressure-transmitting medium.
- High-Pressure Synthesis: The sample was compressed above 33.4 GPa and heated up to approximately 800 K using the BDD heater. Heating and cooling were performed under N2 gas flow to prevent diamond oxidation.
- In Situ Transport Measurement: Sample resistance was continuously monitored during the heating and cooling cycles, revealing a solid-state reaction (irreversible resistance change) and a transition from non-metallic to metallic behavior.
- Structural Analysis: In situ X-ray diffraction (XRD) and Raman spectroscopy were performed during the decompression process (41.1 GPa down to ambient pressure) to confirm the formation of the cubic Sn3S4 phase and determine its stability range.
- Superconductivity Evaluation: Electrical resistance measurements were conducted down to 2 K under various magnetic fields (up to 7 T) to confirm the superconducting transition (Tc) and determine the upper critical field (Bc2).
Commercial Applications
Section titled âCommercial ApplicationsâThe research findings and the developed methodology have implications across several high-technology sectors:
- Novel Materials Discovery: The BDD-integrated DAC is a critical tool for mapping high-pressure/high-temperature phase diagrams and synthesizing new, metastable functional materials (like Sn3S4) that cannot be produced via conventional methods.
- Cryogenic and Superconducting Technology: Sn3S4, as a conventional BCS superconductor with a Tc of 13.3 K, is a candidate material for low-temperature applications, including superconducting wires, magnetic shielding, and sensitive detectors, provided a stable, high-Tc phase can be isolated or stabilized at lower pressures.
- Extreme Environment Sensing and Electronics: The fabrication of robust BDD electrodes, heaters, and thermometers directly on diamond anvils demonstrates a reliable method for creating integrated electronic components capable of operating under extreme pressure and temperature conditions (e.g., geological research, industrial high-pressure reactors).
- Thermoelectric and Phase-Change Materials: The study contributes fundamental data to the Sn-S binary system, which is broadly relevant to materials used in thermoelectric devices (SnSe) and phase-change memory (Sn2Ch3 compounds).
View Original Abstract
High-pressure techniques open exploration of functional materials in broad research fields. An established diamond anvil cell with a boron-doped diamond heater and transport measurement terminals has performed the high-pressure synthesis of a cubic Sn<sub>3</sub>S<sub>4</sub> superconductor. X-ray diffraction and Raman spectroscopy reveal that the Sn<sub>3</sub>S<sub>4</sub> phase is stable in the pressure range of <i>P</i> > 5 GPa in a decompression process. Transport measurement terminals in the diamond anvil cell detect a metallic nature and superconductivity in the synthesized Sn<sub>3</sub>S<sub>4</sub> with a maximum onset transition temperature (<i>T</i><sub>c</sub><sup>onset</sup>) of 13.3 K at 5.6 GPa. The observed pressure-<i>T</i><sub>c</sub> relationship is consistent with that from the first-principles calculation. The observation of superconductivity in Sn<sub>3</sub>S<sub>4</sub> opens further materials exploration under high-temperature and -pressure conditions.