High-pressure Diamond Anvil Cell Research Articles

Thermal conductivity of methanol-ethanol mixture and silicone oil at high pressures

4:1 methanol-ethanol (ME) mixture and silicone oil are common, important pressure transmitting media used in high pressure diamond anvil cell (DAC) experiments. Their thermal conductivities and elastic properties are critical for modeling heat conduction in the DAC experiments and for determining thermal conductivity of measurement samples under extreme conditions. We used time-domain thermoreflectance and picosecond interferometry combined with the DAC to study the thermal conductivities and elastic constants C11 of the ME mixture and silicone oil at room temperature and to pressures as high as ≈23 GPa. We found that pressure dependence of the thermal conductivity of ME and silicone oil are both well described by the prediction of the minimum thermal conductivity model, confirming the diffusion of thermal energy between nonpropagating molecular vibrational modes is the dominant heat transport mechanism in a liquid and amorphous polymer. Our results not only provide new insights into the physics of thermal transport in these common pressure media for high pressure thermal measurements, but will also significantly extend the feasibility of using silicone fluid medium to much higher pressure and moderately high temperature conditions with higher measurement accuracy than other pressure media.

Nuclear resonant inelastic X-ray scattering at high pressure and low temperature.

A new synchrotron radiation experimental capability of coupling nuclear resonant inelastic X-ray scattering with the cryogenically cooled high-pressure diamond anvil cell technique is presented. The new technique permits measurements of phonon density of states at low temperature and high pressure simultaneously, and can be applied to studies of phonon contribution to pressure- and temperature-induced magnetic, superconducting and metal-insulator transitions in resonant isotope-bearing materials. In this report, a pnictide sample, EuFe2As2, is used as an example to demonstrate this new capability at beamline 3-ID of the Advanced Photon Source, Argonne National Laboratory. A detailed description of the technical development is given. The Fe-specific phonon density of states and magnetism from the Fe sublattice in Eu(57)Fe2As2 at high pressure and low temperature were derived by using this new capability.

Viscosity of fluid nitrogen to pressures of 10 GPa.

Shear viscosities of supercritical nitrogen have been measured in the high-pressure diamond-anvil cell, to 673 K and pressures in excess of 10 GPa, using a rolling-sphere technique. The entire set of data, along with lower pressure data from the literature, can be fit to a two-parameter expression in reduced viscosity and reduced residual entropy. The fit spans densities from the dilute gas to 5x the critical density, and two orders magnitude in temperature and in viscosity, with a maximum deviation of 20%. Reduced viscosities scale as ρ(4)/T and comport with the theory of state "isomorphs" for "Roskilde-simple" systems. The new data allow direct comparison with results of molecular dynamic simulations at high densities.

THE ROLE OF CARBON IN EXTRASOLAR PLANETARY GEODYNAMICS AND HABITABILITY

The proportions of oxygen, carbon and major rock-forming elements (e.g. Mg, Fe, Si) determine a planet's dominant mineralogy. Variation in a planet's mineralogy subsequently affects planetary mantle dynamics as well as any deep water or carbon cycle. Through thermodynamic models and high pressure diamond anvil cell experiments, we demonstrate the oxidation potential of C is above that of Fe at all pressures and temperatures indicative of 0.1 - 2 Earth-mass planets. This means that for a planet with (Mg+2Si+Fe+2C)/O > 1, excess C in the mantle will be in the form of diamond. We model the general dynamic state of planets as a function of interior temperature, carbon composition, and size, showing that above a critical threshold of $\sim$3 atom% C, limited to no mantle convection will be present assuming an Earth-like geotherm. We assert then that in the C-(Mg+2Si+Fe)-O system, only a very small compositional range produce habitable planets. Planets outside of this habitable range will be dynamically sluggish or stagnant, thus having limited carbon or water cycles leading to surface conditions inhospitable to life as we know it.

Formula omitted]-bearing post-perovskite in the Earth's lower mantle

The combined effects of Fe and Al on the electronic spin and valence states as well as the equation of state (EoS) of post-perovskite have been investigated using synchrotron X-ray diffraction and Mössbauer spectroscopy in high-pressure diamond anvil cells. Two post-perovskite samples (Mg0.6Fe0.15Al0.5Si0.75O3 and Mg0.66Fe0.13Al0.28Si0.86O3) were synthesized at approximately 165 GPa and 2200–2500 K, and were subsequently investigated for these properties at 114–170 GPa and 300 K. Analyses of the high-pressure Mössbauer spectra show that Fe2+ and Fe3+ occupy the large bipolar prismatic sites in both of our samples and remain in the high-spin state at ∼165–168 GPa and 300 K. Combining the Mössbauer results with the obtained pressure–volume relationship from X-ray diffraction, we have found that the unit cell volume of post-perovskite can be significantly affected by the spin and valence states of Fe and the Al substitution. Mg0.6Fe0.15Al0.5Si0.75O3–PPv with the predominantly high-spin Fe2+ (∼95%) and a greater amount of Al has a unit cell volume similar to that of Mg0.66Fe0.13Al0.28Si0.86O3–PPv in which ∼65% of Fe is in the high-spin Fe3+ state. Our results are used together with previous results regarding the EoS parameters in Fe-bearing perovskite and post-perovskite to model the density and bulk sound velocity variation between perovskite and post-perovskite in the D″ layer, in which the enrichment of Fe and Al can produce an increase in density but substantially reduce the bulk sound velocity across the phase transition. That is, the combined effect of Fe and Al leads to an anti-correlation between the enhanced density and the reduced bulk sound velocity at the pressure condition of the lowermost mantle. Our results indicate that (Fe,Al)-rich silicate post-perovskite existing in the D″ region would be shown as a relatively high-density and low-velocity region in deep-mantle seismic observations.

New high-pressure van der Waals compound Kr(H2)4 discovered in the krypton-hydrogen binary system

AbstractThe application of pressure to materials can reveal unexpected chemistry. Under compression, noble gases form stoichiometric van der Waals (vdW) compounds with closed-shell molecules such as hydrogen, leading to a variety of unusual structures. We have synthesised Kr(H2)4 for the first time in a diamond-anvil high-pressure cell at pressures ≥5.3 GPa and characterised its structural and vibrational properties to above 50 GPa. The structure of Kr(H2)4, as solved by single-crystal synchrotron X-ray diffraction, is face-centred cubic (fcc) with krypton atoms forming isolated octahedra at fcc sites. Rotationally disordered H2 molecules occupy four different, interstitial sites, consistent with the observation of four Raman active H2 vibrons. The discovery of Kr(H2)4 expands the range of pressure-stabilised, hydrogen-rich vdW solids, and, in comparison with the two known rare-gas-H2 compounds, Xe(H2)8 and Ar(H2)2, reveals an increasing change in hydrogen molecular packing with increasing rare gas atomic number.

Magnetic and structural transitions of SrFe2As2 at high pressure and low temperature

One of key issues in studying iron based superconductors is to understand how the magnetic phase of the parent compounds evolves. Here we report the systematic investigation of paramagnetic to antiferromagnetic and tetragonal to orthorhombic structural transitions of “122” SrFe2As2 parent compound using combined high resolution synchrotron Mössbauer spectroscopy and x-ray diffraction techniques in a cryogenically cooled high pressure diamond anvil cell. It is found that although the two transitions are coupled at 205 K at ambient pressure, they are concurrently suppressed to much lower temperatures near a quantum critical pressure of approximately 4.8 GPa where the antiferromagnetic state transforms into bulk superconducting state. Our results indicate that the lattice distortions and magnetism jointly play a critical role in inducing superconductivity in iron based compounds.

Sound velocities of vanadium under shock compression

A series of reverse-impact experiments is performed on vanadium at peak shock pressures from 32 GPa to 88 GPa. A displacement interferometer is used to measure the particle velocity profile at the vanadium/LiF window interface. Analysis of these profile provides a measure of sound velocity of vanadium in the Hugoniot state. The transition from body-centered cubic structure to rhombohedral structure phase at ～ 60 GPa is identified by the discontinuity of the sound velocity against shock pressure. This transition pressure is consistent with the data from high pressure diamond anvil cell experiments and first-principle calculations.

Pressure-induced structural evolution and amorphization in Eu3Ga5O12

Crystal structural evolution of europium gallium garnet (Eu3Ga5O12; EGG) has been investigated by a combination of synchrotron x-ray diffraction, Raman scattering, and photoluminescence spectroscopy in a high-pressure diamond anvil cell. The cubic garnet EGG mostly collapses into an amorphous state upon compression to 85 GPa at room temperature. High-pressure Raman and photoluminescence spectra indicate that the amorphization process is related to the interaction and deformation of the tetrahedra GaO4 and octahedra GaO6 under compression, leading to the increase of the asymmetry of the local oxygen environment around the Eu3+ site with increasing pressures. The amorphization of EGG is associated with the overlapping of the tetrahedra and octahedra and the increase of the average coordination numbers of the Ga3+ ions in the amorphous state. X-ray diffraction spectra of EGG taken from a laser-heated diamond anvil cell demonstrate that the pressure-induced garnet-to-amorphous transition could result from the kinetic hindrance of a crystal-to-crystal phase transition at room temperature, rather than the decomposition reported earlier.

Note: Compact optical fiber coupler for diamond anvil high pressure cells

A compact optical fiber coupler has been developed to allow transmission of light through an optical fiber to and from the high pressure region of a diamond anvil high pressure cell. Despite its small size the coupler has focusing adjustments and optics, which allows the light to be focused precisely on the sample within the pressure cell. The coupler is suitable for a wide range of optical measurements and particularly for high pressure measurements at low temperatures in cryostats with no optical windows. The use of the coupler to determine the pressure in a diamond anvil cell at 1.2 K using the ruby fluorescence spectra of ruby is demonstrated. The small size of the coupler and its construction out of nonmagnetic beryllium copper makes it suitable for use in high magnetic fields and for magnetization experiments.

High-temperature experiments using a resistively heated high-pressure membrane diamond anvil cell

We describe a reliable high performance resistive heating method developed for the membrane diamond anvil cell. This method generates homogenous high temperatures at high pressure in the whole sample for extended operation period. It relies on two mini coil heaters made of Pt-Rh alloy wire mounted around the diamond anvils and gasket, while temperature is monitored by two K-type thermocouples mounted near the sample. The sample, diamonds, and tungsten-carbide seats are thermally insulated from the piston and cylinder keeping the cell temperature below 750 K while the sample temperature is 1200 K. The cell with the heaters is placed in a vacuum oven to prevent oxidation and unnecessary heat loss. This assembly allows complete remote operation, ideally suited for experiments at synchrotron facilities. Capabilities of the setup are demonstrated for in situ Raman and synchrotron x-ray diffraction measurements. We show experimental measurements from isothermal compression at 900 K and 580 K to 100 GPa and 185 GPa, respectively, and quasi-isobaric compression at 95 GPa over 1000 K.

Superelastic carbon spheres under high pressure

We report a superelastic deformation behavior of carbon spheres by the in situ Raman spectroscopy in a high-pressure diamond anvil cell. The carbon spheres produced by arc discharging in toluene have a mean diameter of 200 nm and an onion-like multilayer graphitic structure. We find that the elastic coefficients, during both the compression and decompression processes, remain a constant up to 10 GPa, indicating a superior high-pressure structural stability. Such superelastic behavior is related to the isotropic and concentric configuration of carbon spheres and provides additional insight into improving the microscopic mechanical properties of small-scale particles.

How “Hollow” Are Hollow Nanoparticles?

Diamond anvil cell (DAC), synchrotron X-ray diffraction (XRD), and small-angle X-ray scattering (SAXS) techniques are used to probe the composition inside hollow γ-Fe(3)O(4) nanoparticles (NPs). SAXS experiments on 5.2, 13.3, and 13.8 nm hollow-shell γ-Fe(3)O(4) NPs, and 6 nm core/14.8 nm hollow-shell Au/Fe(3)O(4) NPs, reveal the significantly high (higher than solvent) electron density of the void inside the hollow shell. In high-pressure DAC experiments using Ne as pressure-transmitting medium, formation of nanocrystalline Ne inside hollow NPs is not detected by XRD, indicating that the oxide shell is impenetrable. Also, FTIR analysis on solutions of hollow-shell γ-Fe(3)O(4) NPs fragmented upon refluxing shows no evidence of organic molecules from the void inside, excluding the possibility that organic molecules get through the iron oxide shell during synthesis. High-pressure DAC experiments on Au/Fe(3)O(4) core/hollow-shell NPs show good transmittance of the external pressure to the gold core, indicating the presence of the pressure-transmitting medium in the gap between the core and the hollow shell. Overall, our data reveal the presence of most likely small fragments of iron and/or iron oxide in the void of the hollow NPs. The iron oxide shell seems to be non-porous and impenetrable by gases and liquids.

High-pressure effects on single crystals of electron-doped Pr2−xCexCuO4

We present high pressure diamond anvil cell synchrotron X-ray, resistivity, and ac-susceptibility measurements on electron-doped cuprate Pr$_{2-x}$Ce$_{x}$CuO$_{4}$ to much higher pressures than previously reported. At 2.72 GPa between 88 and 98$%$ of the superconducting T$^\prime$ phase \cite{Tprime} of the optimally doped Pr$_{1.85}$Ce$_{0.15}$CuO$_{4}$ transforms into the insulating phase T. The T$_{c}$ of the remaining 2-12$%$ T$^\prime$ phase is suppressed continuously from 22 K to 18.5 K at about 14 GPa. Remarkably, the T$_{c}$ of the over doped Pr$_{1.83}$Ce$_{0.17}$CuO$_{4}$ remains practically unchanged even at 32 GPa. This behavior of the electron-doped cuprate contrasts with that of the hole-doped cuprate for which T$_{c}$ is first substantially enhanced with applied pressure.

Refractive index and compressibility of Di64An36 glass over a pressure range of 0–5.0 GPa

Data on the refractive index, density, and bulk modulus variations of Di64An36 glass, which is used as a model basalt melt, were obtained with a polarization interference microscope and a high-pressure diamond anvil cell at ambient temperature and pressure up to 5.0 GPa. An anomalous decrease in the bulk modulus, Kt, was observed in the pressure range 0–1.0 GPa. The values of the zero-pressure isothermal bulk modulus, Kt,0 = 22.2, and variation of the bulk modulus with pressure, ΔKt/ΔP = 11.35, were derived using a linear equation relating Kt and P over the pressure range with the normal behavior of the compressibility. A comparison of our results with previous data on other glasses and melts showed that the bulk moduli of silicate glasses are similar to those of corresponding melts. The values of the pressure coefficient of the bulk moduli, ΔKt/ΔP, for glasses derived from linear equations are 2.5 times higher than the pressure derivative of the bulk modulus, K′T, derived using the Birch-Murnaghan equation for corresponding melts. The difference in ΔKt/ΔP and K′T has an effect on the compressibility of glasses and melts. The compressibility of glasses up to 5.0 GPa calculated as (d − d0)/d is almost two times lower than that of corresponding melts.

High-pressure diamond anvil cell studies of carbon monoxide – viscosity, photochemical polymerization and laser heating

High-pressure diamond anvil cell studies of carbon monoxide – viscosity, photochemical polymerization and laser heating

In Situ Observation of Multiple Phase Transitions in Low-Melting Ionic Liquid [BMIM][BF4] under High Pressure up to 30 GPa

In situ characterization of phase transitions and direct microscopic observations of a low-melting ionic liquid, 1-butyl-3-methyl imidazolium tetrafluoroborate ([BMIM][BF(4)]), has been performed in detail by Raman spectroscopy. Compression of [BMIM][BF(4)] was measured under hydrostatic pressure up to ~30.0 GPa at room temperature by using a high-pressure diamond anvil cell. With pressure increasing, the characteristic bands of [BMIM][BF(4)] displayed nonmonotonic pressure-induced frequency shifts, and it is found to undergo four successive phase transitions at around 2.25, 6.10, 14.00, and 21.26 GPa. Especially, above a pressure of 21.26 GPa, luminescence of the sample occurs, which is connected with the most significant phase transition at around this pressure. It was indicated that the structure change under high pressure might be associated with a conformational change in the butyl chain. Upon releasing pressure, the spectrum was not recovered under a pressure up to 1.16 GPa, thereby indicating that this high-pressure phase remains stable over a large pressure range between 30 and 1.16 GPa in low-melting ionic liquid [BMIM][BF(4)]. Although the sample was kept under the normal pressure for 24 h, the spectrum was recovered, and it showed that the phase transition of [BMIM][BF(4)] was reversible. In other words, such a low-melting ionic liquid [BMIM][BF(4)] remains stable even after being treated under so a high pressure of up to 30 GPa.

Determination of the thickness of a gasket in a diamond anvil high-pressure cell

A method for determining the thickness of a gasket in a diamond anvil high-pressure cell is described. This method is based on measuring the relative position of the anvils. The gasket thickness is determined by measuring the distance between two marks, viz., virtual points “locked” to side surfaces of the anvils. The distance between the marks is determined by digital processing of microphotographs. The error of measuring the gasket thickness disregarding the deformations of the anvils is ∼1 μm. The results of measuring the gasket thickness, the aperture area, and the optical length between the working planes of the anvils for a helium-filled cell are presented. The pressure dependences of the refractive index and the volume of helium, which is compressed to a pressure of 16 GPa, that are calculated using these data are in good agreement with the published data.

Conducting boron-doped single-crystal diamond films for high pressure research

Epitaxial boron-doped diamond films were grown by microwave plasma chemical vapor deposition for application as heating elements in high pressure diamond anvil cell devices. To a mixture of hydrogen, methane and oxygen, diborane concentrations of 240–1200 parts per million were added to prepare five diamond thin-film samples. Surface morphology has been observed to change depending on the amount of diborane added to the feed gas mixture. Single-crystal diamond film with a lowest room temperature resistivity of 18 mΩ cm was fabricated and temperature variation of resistivity was studied to a low temperature of 12 K. The observed minima in resistivity values with temperature for these samples have been attributed to a change in conduction mechanism from band conduction to hopping conduction. We also present a novel fabrication methodology for monocrystalline electrically conducting channels in diamond and present preliminary heating data with a boron-doped designer diamond anvil to 620 K at ambient pressure.

Multipurpose high-pressure high-temperature diamond-anvil cell with a novel high-precision guiding system and a dual-mode pressurization device

A novel diamond-anvil cell (DAC) design has been constructed and tested for in situ applications at high-pressure (HP) operations and has proved to be suitable even for HP sample environments at non-ambient temperature conditions. The innovative high-precision guiding mechanism, comparable to a dog clutch, consists of perpendicular planar sliding-plane elements and is integrated directly into the base body of the cylindrically shaped DAC. The combination of two force-generating devices, i.e., mechanical screws and an inflatable gas membrane, allows the user to choose independently between, and to apply individually, two different forcing mechanisms for pressure generation. Both mechanisms are basically independent of each other, but can also be operated simultaneously. The modularity of the DAC design allows for an easy exchange of functional core-element groups optimized not only for various analytical in situ methods but also for HP operation with or without high-temperature (HT) application. For HP-HT experiments a liquid cooling circuit inside the specific inner modular groups has been implemented to obtain a controlled and limited heat distribution within the outer DAC body.