Characteristics of silicone fluid as a pressure transmitting medium in diamond anvil cells

Shen, Yongrong; Kumar, Ravhi S.; Pravica, Michael; Nicol, Malcolm

doi:10.1063/1.1786355

Cited by 129 publications

(63 citation statements)

References 31 publications

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“…To recover the edge energy of the initial point at 15 GPa, the pressure has to be released down to about 5 GPa. Even if some deviatoric stress effects might exist and lead to some strain in the small poly crystalline grains 26,27 , these effects should be smaller than the observed bond length hysteresis (≈ 0.05Å or 2.5%) in the 10 to 15 GPa range. Zhao and coworkers 32 found in a similar compound a highest strain difference of 0.3% at 6 GPa originating from silicone oil at non-hydrostatic conditions.…”

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confidence: 83%

Bandwidth-driven nature of the pressure-induced metal state of LaMnO ₃

Ramos

Souza-Neto

Tolentino

et al. 2011

EPL

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Using X-ray absorption spectroscopy (XAS), we studied the local structure in LaMnO3 under applied pressure across and well above the insulator to metal (IM) transition. A hysteretic behavior points to the coexistence of two phases within a large pressure range (7 to 25 GPa). The ambient phase with highly Jahn-Teller (JT) distorted M nO6 octahedra is progressively substituted by a new phase with less-distorted JT M nO6 units. The electronic delocalization leading to the IM transition is finger-printed from the pre-edge XAS structure around 30 GPa. We observed that the phase transition takes place without any significant reduction of the JT distortion. This entails band-overlap as the driving mechanism of the IM transition.PACS numbers: 61.50. Ks,71.70.Ej, 71.30.+h LaMnO 3 is the parent compound of a family of doped manganates that exhibit a multitude of electronic phases and unusual properties with strong potential for new electronic devices 1 . The compound crystallizes in the orthorhombically distorted perovskite structure (space group Pbmn), in which every M n 3+ ion with high-spin configuration tis surrounded by an octahedron of six oxygen ligands. Under ambient conditions, the Jahn-Teller (JT ) instability of the singly occupied e g orbitals gives rise to cooperative distortions of the M nO 6 octahedra, which induce orbital ordering and may be responsible for the insulating behavior of LaMnO 3 . Although the ground-state of LaMnO 3 can be explained both by cooperative JT distortion and orbital exchange interaction, their relative importance lead to different physics for the doped systems and is then an important issue for predicting and optimizing physical properties. However, the separation of the two effects is a very delicate issue 2-8 that calls for accurate experimental probes.At ambient pressure LaMnO 3 undergoes at T IM =710 K an insulator to metal (IM) transition, structurally described as a transition from an ordered toward a disordered array of JT distorted octahedra. The long range structure is characterized by a strong cell symmetrization and the loss of the orbital order 9 . The local scale JT splitting persists essentially unaltered across the IM transition, which is marked by the symmetrization of the thermal fluctuations in the distorted M nO 6 units 10,11 .At ambient temperature, transition towards a metal state can also be attained by application of external hydrostatic pressure. High pressure reduces lattice parameters, favoring orbital overlap and concomitant enhancement of electron delocalization. It also forces an atomic rearrangement, tending to reduce lattice distortions (inter-octahedral and intra-octahedra rearrangements). In LaMnO 3 the IM transition has been reported by Loa and coworkers at an applied pressure of 32 GPa 12 . Using X-ray diffraction under pressure, these authors obtained refined atomic positions up to 11 GPa 12 . From an extrapolation of their results, they predict that the local JT distortion should completely vanish around 18 GPa. However, in a previous X-ray ...

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confidence: 83%

Bandwidth-driven nature of the pressure-induced metal state of LaMnO ₃

Ramos

Souza-Neto

Tolentino

et al. 2011

EPL

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“…In the membrane DAC, samples were loaded in 150-µm-holes drilled in Inconel gaskets and in the Boehler-Almax DAC in 100-µm-holes drilled in tungsten gaskets. Silicone oil was used as pressure-transmitting medium [12,13] and the pressure was measured by means of the ruby fluorescence technique [14]. A pinhole placed before the sample position was used as a clean-up aperture for filtering out the tail of the focused x-ray beam.…”

Section: Methodsmentioning

confidence: 99%

High-pressure phase transitions and compressibility of wolframite-type tungstates

Ruiz‐Fuertes

López-Moreno

Errandonea

et al. 2010

Journal of Applied Physics

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This paper reports an investigation on the phase diagram and compressibility of wolframite-type tungstates by means of x-ray powder diffraction and absorption in a diamondanvil cell and ab initio calculations. The diffraction experiments show that monoclinic wolframite-type MgWO 4 suffers at least two phase transitions, the first one being to a triclinic polymorph with a structure similar to that of CuWO 4 and FeMoO 4 -II. The onset of each transition is detected at 17.1 and 31 GPa. In ZnWO 4 the onset of the monoclinic-triclinic transition has been also found at 15.1 GPa. These findings are supported by density-functional theory calculations, which predict the occurrence of additional transitions upon further compression. Calculations have been also performed for wolframite-type MnWO 4 , which is 2 found to have an antiferromagnetic configuration. In addition, x-ray absorption and diffraction experiments as well as calculations reveal details of the local-atomic compression in the studied compounds. In particular, below the transition pressure the ZnO 6 and equivalent polyhedra tend to become more regular, whereas the WO 6 octahedra remain almost unchanged.

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“…[17] Previous studies have shown that pressure gradients result in broadening of the R 1 ruby line [Chai and Brown, 1996;Shen et al, 2004]. An increase in the R 1 À R 2 separation is indicative of the development of deviatoric stress because the wavelength of R 2 is only sensitive to the local mean stress while R 1 is affected by deviatoric stress in the sample [Chai and Brown, 1996;Shen et al, 2004].…”

Section: Discussionmentioning

confidence: 99%

“…An increase in the R 1 À R 2 separation is indicative of the development of deviatoric stress because the wavelength of R 2 is only sensitive to the local mean stress while R 1 is affected by deviatoric stress in the sample [Chai and Brown, 1996;Shen et al, 2004]. Therefore, the steep increase in the FWHM of the R 1 ruby line and the R 1 À R 2 separation to about 9 GPa without a pressure medium indicate increases in both the pressure gradients and the deviatoric stress with P. The flattening, or even decrease in the values, occur over the P range reported for the amorphization of non-hydrostatically loaded Ca(OH) 2 [Meade and Jeanloz, 1990;Nagai et al, 2000].…”

Section: Discussionmentioning

confidence: 99%

A crystalline‐to‐crystalline phase transition in Ca(OH)₂ at 8 GPa and room temperature

Catalli

Shim

Prakapenka

2008

Geophysical Research Letters

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X‐ray diffraction and Raman spectroscopy measurements reveal that Ca(OH)2‐portlandite transforms to a crystalline phase with an ordered OH sublattice between 8 and 14 GPa at room temperature under quasi‐hydrostatic stress conditions in an Ar pressure medium. The amorphization previously reported at 11 GPa under no pressure medium was not observed up to 26 GPa. The width and separation of the fluorescence peaks from the ruby chips embedded in Ca(OH)2 without a medium suggest that deviatoric stress is responsible for the previously observed amorphization. Our study demonstrates that the behavior of hydrous phases in the subducting slab could be sensitive to local deviatoric stresses. Together with similar reports on quartz, our observation on Ca(OH)2 indicates that deviatoric stress is an important factor to consider for P‐induced amorphization reported in a wide range of materials.

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Characteristics of silicone fluid as a pressure transmitting medium in diamond anvil cells

Cited by 129 publications

References 31 publications

Bandwidth-driven nature of the pressure-induced metal state of LaMnO ₃

Bandwidth-driven nature of the pressure-induced metal state of LaMnO ₃

High-pressure phase transitions and compressibility of wolframite-type tungstates

A crystalline‐to‐crystalline phase transition in Ca(OH)₂ at 8 GPa and room temperature

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Characteristics of silicone fluid as a pressure transmitting medium in diamond anvil cells

Cited by 129 publications

References 31 publications

Bandwidth-driven nature of the pressure-induced metal state of LaMnO 3

Bandwidth-driven nature of the pressure-induced metal state of LaMnO 3

High-pressure phase transitions and compressibility of wolframite-type tungstates

A crystalline‐to‐crystalline phase transition in Ca(OH)2 at 8 GPa and room temperature

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Product

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Bandwidth-driven nature of the pressure-induced metal state of LaMnO ₃

Bandwidth-driven nature of the pressure-induced metal state of LaMnO ₃

A crystalline‐to‐crystalline phase transition in Ca(OH)₂ at 8 GPa and room temperature