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This work focuses on the standard protocol for preparing the externally-heated diamond anvil cell (EHDAC) for generating high-pressure and high-temperature (HPHT) conditions. The EHDAC is employed to investigate materials in Earth and planetary interiors under extreme conditions, which can be also used in solid state physics and chemistry studies.
The externally-heated diamond anvil cell (EHDAC) can be used to generate simultaneously high-pressure and high-temperature conditions found in Earth’s and planetary interiors. Here we describe the design and fabrication of the EHDAC assemblies and accessories, including ring resistive heaters, thermal and electrical insulating layers, thermocouple placement, as well as the experimental protocol for preparing the EHDAC using these parts. The EHDAC can be routinely used to generate megabar pressures and up to 900 K temperatures in open air, and potentially higher temperatures up to ~1200 K with a protective atmosphere (i.e., Ar mixed with 1% H2). Compared with a laser-heating method for reaching temperatures typically >1100 K, external heating can be easily implemented and provide a more stable temperature at ≤900 K and less temperature gradients to the sample. We showcased the application of the EHDAC for synthesis of single crystal ice-VII and studied its single-crystal elastic properties using synchrotron-based X-ray diffraction and Brillouin scattering at simultaneously high-pressure high-temperature conditions.
The diamond anvil cell (DAC) is one of the most important tools for high pressure research. Coupled with synchrotron-based and conventional analytical methods, it has been widely used to study properties of planetary materials up to multi-megabar pressures and at wide ranges of temperatures. Most planetary interiors are under both high-pressure and high-temperature (HPHT) conditions. It is thus essential to heat the compressed samples in a DAC at high pressures in situ to study the physics and chemistry of planetary interiors. High temperatures are not only required for the investigations of phase and melting relationships and thermodynamic properties of planetary materials, but also help mitigate pressure gradient, promote phase transitions and chemical reactions, and expedite diffusion and recrystallization. Two methods are typically utilized to heat the samples in DACs: laser-heating and internal/external resistive heating methods.
The laser-heated DAC technique has been employed for high-pressure materials science and mineral physics research of planetary interiors1,2. Although increasing number of laboratories have access to the technique, it usually requires significant development and maintenance effort. The laser heating technique has been used to achieve temperatures as high as 7000 K3. However, long-duration stable heating as well as temperature measurement in laser-heating experiments have been a persistent issue. The temperature during laser heating usually fluctuates but can be mitigated by feed-back coupling between thermal emission and laser power. More challenging is controlling and determining the temperature for assembly of multiple phases of different laser absorbance. The temperature also has a considerably large gradient and uncertainties (hundreds of K), although recent technical development effort has been used to mitigate this issue4,5,6. Temperature gradients in the heated sample area sometimes may further introduce chemical heterogeneities caused by diffusion, re-partitioning or partial melting. In addition, temperatures less than 1100 K typically could not be measured precisely without customized detectors with high sensitivity in the infrared wavelength range.
The EHDAC uses resistive wires or foils around the gasket/seat to heat the entire sample chamber, which provides the ability of heating the sample to ~900 K without a protective atmosphere (such as Ar/H2 gas) and to ~1300 K with a protective atmosphere7. The oxidation and graphitization of diamonds at higher temperatures limit the highest achievable temperatures using this method. Although the temperature range is limited compared with laser-heating, it provides more stable heating for a long duration and a smaller temperature gradient8, and is well suited to be coupled with various detection and diagnostic methods, including optical microscope, X-ray diffraction (XRD), Raman spectroscopy, Brillouin spectroscopy and Fourier-transform infrared spectroscopy9. Therefore, the EHDAC has become a useful tool to study various material properties at HPHT conditions, such as phase stability and transitions10,11, melting curves12, thermal equation of state13, and elasticity14.
The BX-90 type DAC is a newly developed piston-cylinder type DAC with large aperture (90° at maximum) for XRD and laser spectroscopy measurements9, with the space and openings to mount a miniature resistive heater. The U-shaped cut on the cylinder side also provides room to release the stress between the piston and the cylinder side caused by temperature gradient. Therefore, it has recently been widely used in powder or single-crystal XRD and Brillouin measurements with the external-heating setup. In this study, we describe a reproducible and standardized protocol for preparing EHDACs and demonstrated single-crystal XRD as well as Brillouin spectroscopy measurements of synthesized single-crystal ice-VII using the EHDAC at 11.2 GPa and 300-500 K.
1. Ring heater preparation
2. EHDAC preparation
3. Synthesizing single-crystal ice-VII by EHDAC
4. Synchrotron X-ray diffraction and Brillouin spectroscopy collection
In this report, we used the fabricated resistive micro-heater and BX-90 DAC for the EHDAC experiment (Figure 1 and Figure 2). Figure 1 shows the machining and fabrication processes of the ring heaters. The standard dimensions of the heater base are 22.30 mm in outer diameter, 8.00 mm in inner diameter and 2.25 mm in thickness. The dimensions of the ring heater can be adjusted to accommodate various types of seats and diamonds.<...
In this work, we described the protocol of preparing the EHDAC for high pressure research. The cell assemblies including a micro-heater and thermal and electrical insulating layers. Previously, there are multiple designs of resistive heaters for different types of DACs or experimental configurations7,17,18,19,20. Most of the heaters are machined by individual ...
The authors declare no conflict of interest.
We thank Siheng Wang, Qinxia Wang, Jing Gao, Yingxin Liu for their help with the experiments. This research used resources of the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. GeoSoilEnviroCARS (Sector 13) is supported by NSF-Earth Sciences (EAR-1128799), and the Department of Energy, Geosciences (DE-FG02-94ER14466). The development of EHDAC was supported by Externally-heated Diamond Anvil Cell Experimentation (EH-DANCE) project to B. Chen under Education Outreach and Infrastructure Development (EOID) program from COMPRES under NSF Cooperative Agreement EAR-1606856. X. Lai acknowledges the support from the start-up funding of China University of Geosciences (Wuhan) (no.162301202618). B. Chen acknowledges the support from the U.S. National Science Foundation (NSF) (EAR-1555388 and EAR-1829273). J.S. Zhang acknowledges the support from the U.S. NSF (EAR-1664471, EAR-1646527 and EAR-1847707).
Name | Company | Catalog Number | Comments |
Au | N/A | N/A | for pressure calibration |
Deionized water | Fisher Scientific | 7732-18-5 | for the starting material of ice-VII synthesis |
Diamond anvil cell | SciStar, Beijing | N/A | for generating high pressure |
K-type thermocouple | Omega | L-0044K | for measuring high temperature |
Mica | Spruce Pine Mica Company | N/A | for electrical insulation |
Pt 10wt%Rh | Alfa Aesar | 10065 | for heater |
Pyrophyllite | McMaster-Carr | 8479K12 | for fabricating the heater base |
Re | Sigma-Aldrich | 267317 | for the gasket of diamond anvil cell |
Resbond 919 Ceramic Adhesive | Cotronics Corp | Resbond 919-1 | for insulating heating wires and mounting diamonds on seats |
Ruby | N/A | N/A | for pressure calibration |
Ultra-Temp 2300F ceramic tape | McMaster Carr Supply | 390-23M | for thermal insulation |
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