BX90: A new diamond anvil cell design for X-ray diffraction and opticalmeasurementsI. Kantor, V. Prakapenka, A. Kantor, P. Dera, A. Kurnosov et al. Citation: Rev. Sci. Instrum. 83, 125102 (2012); doi: 10.1063/1.4768541 View online: http://dx.doi.org/10.1063/1.4768541 View Table of Contents: http://rsi.aip.org/resource/1/RSINAK/v83/i12 Published by the American Institute of Physics. Related ArticlesOxy-acetylene driven laboratory scale shock tubes for studying blast wave effects Rev. Sci. Instrum. 83, 045111 (2012) Pressure distribution in a quasi-hydrostatic pressure medium: A finite element analysis J. Appl. Phys. 110, 113523 (2011) Multipurpose high-pressure high-temperature diamond-anvil cell with a novel high-precision guiding system anda dual-mode pressurization device Rev. Sci. Instrum. 82, 095108 (2011) A high temperature high pressure cell for quasielastic neutron scattering Rev. Sci. Instrum. 82, 083903 (2011) Accurate measurement of sample conductivity in a diamond anvil cell with axis symmetrical electrodes and finitedifference calculation AIP Advances 1, 032116 (2011) Additional information on Rev. Sci. Instrum.Journal Homepage: http://rsi.aip.org Journal Information: http://rsi.aip.org/about/about_the_journal Top downloads: http://rsi.aip.org/features/most_downloaded Information for Authors: http://rsi.aip.org/authors

REVIEW OF SCIENTIFIC INSTRUMENTS 83, 125102 (2012)

BX90: A new diamond anvil cell design for X-ray diffractionand optical measurements

I. Kantor,1 V. Prakapenka,2 A. Kantor,1,3 P. Dera,2 A. Kurnosov,3 S. Sinogeikin,4

N. Dubrovinskaia,5 and L. Dubrovinsky3

1European Synchrotron Radiation Facility, 38043 Grenoble, BP 220, France2GSECARS, University of Chicago, Illinois 60437, USA3Bayerisches Geoinstitut, University of Bayreuth, 95440 Bayreuth, Germany4HPCAT, Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20005, USA5Material Physics and Technology at Extreme Conditions, Laboratory of Crystallography,University of Bayreuth, 95440 Bayreuth, Germany

(Received 12 August 2012; accepted 6 November 2012; published online 5 December 2012)

We present a new design of a universal diamond anvil cell, suitable for different kinds of experimen-tal studies under high pressures. Main features of the cell are an ultimate 90-degrees symmetricalaxial opening and high stability, making the presented cell design suitable for a whole range of tech-niques from optical absorption to single-crystal X-ray diffraction studies, also in combination withexternal resistive or double-side laser heating. Three examples of the cell applications are provided:a Brillouin scattering of neon, single-crystal X-ray diffraction of α-Cr2O3, and resistivity measure-ments on the (Mg0.60Fe0.40)(Si0.63Al0.37)O3 silicate perovskite. © 2012 American Institute of Physics.[http://dx.doi.org/10.1063/1.4768541]

I. INTRODUCTION

For more than fifty years, diamond-anvil cells (DACs) re-main one of the major tools for static high-pressure studiesin geosciences, physics, and related fields. A wide range ofdifferent experimental techniques has been applied in inves-tigations with a DAC, starting from simple optical observa-tions to various types of absorption, reflection, emission, andscattering of all kinds of electromagnetic radiation in a widerange of photon energies. Several megabars pressures can bereached and with the use of cryostats, external ovens and re-sistive heaters or laser heating temperature can also be variedin a wide range from several milli-Kelvins to thousands ofdegrees. All these possibilities make DAC a unique apparatuscapable of covering a huge part of the P-T space unreachablewith any other experimental technique. A brilliant historicaloverview of a diamond anvil cell appearance, principal de-sign, and major application fields can be found in the paper ofBassett.1

Because of such a wide range of experimental techniques,there is also quite a wide range of DAC designs. By thedriving force, DACs can be divided into two main groups:screwing type and gas-membrane type. In the first type, load-ing force is created by tightening screws directly onto dia-mond anvils or through a system of levers, arms, or wedges(Jayaraman2). In the second type, force is created by adjustingthe pressure of a gas filling a metallic membrane that pushestwo parts of the cell towards each other. Both types have theirstrong and weak sides: in general, screw-driven DACs havesimpler and thus more reliable construction; they can easilymaintain pressure if a DAC needs to be moved from place toplace or stored for a long time; they have more predictablebehavior upon heating or cooling; they can be more compact;there is no need of a metal capillary tube and attached gas con-troller. Gas-membrane DACs give more accurate control over

pressure in the sample chamber and allow remote pressureadjustment without touching and moving a DAC that some-times extremely helpful during an experiment. Other DACtypes such as piezo-driven or oil hydraulic type are extremelyrare.

A successful use of a DAC requires that two diamonds re-main strictly coaxial and perfectly aligned against each other.To ensure such a parallel movement of two diamond anvils,traditionally two main designs have been used: a piston-cylinder type, where one diamond anvil is attached to a pis-ton moving inside a perfectly matching cylinder carrying theother anvil, or a plate-type with special guiding pins, suchas a Merrill-Bassett design (Merrill and Bassett3). A piston-cylinder design is believed to be more stable and reliable,though usually the cells are more massive that limits a pos-sibility to increase the DAC opening angle. Recently, an-other type of DAC design was proposed by Boehler,4 wherethe force between anvils is created by bending two 5-mmthick steel discs. Such a design makes it much easier tomanufacture the cell, because no ultra-fine machining is re-quired. A serious disadvantage of this design is a smallefficiency—a huge part of force created by screws is used tobend steel plates, rather than increase pressure in the sam-ple chamber, making the whole system very sensitive to smallmisalignments or temperature gradients in case of externalheating.

II. DAC DESIGN

Different experimental techniques have different require-ments for a DAC size and geometry. Typically, DAC design isa compromise between size, stability, and axial and side open-ing of the cell. A main goal for this work was to create a sim-ple piston-cylinder-type cell with a wide (90◦) symmetrical

0034-6748/2012/83(12)/125102/6/$30.00 © 2012 American Institute of Physics83, 125102-1

125102-2 Kantor et al. Rev. Sci. Instrum. 83, 125102 (2012)

FIG. 1. BX90 diamond anvil cell design. (a) Section view, (b) photographof a loaded cell, (c) exploded view. (1) Outer cylinder part, (2) inner pistonpart, (3) diamond supporting plates, (4) diamond anvils, (5) metallic gasket,(6) M4 (#8-32) screws for generating loading force, (7) pack of conical springwashers (Belleville springs), (8) setscrews for diamond anvils alignment,(9) safety setscrews, (10) optional miniature resistive heater.

conical axial opening from both sides, suitable for powder andsingle-crystal X-ray diffraction with double-sided laser heat-ing (Shen et al.5), Brillouin spectroscopy (Sinogeikin et al.6),and other techniques requiring access to the pressure cham-ber from different directions. The cell was named “BX90,” anacronym for Brillouin scattering–X-ray diffraction with a 90◦

opening angle.A major advantage of the BX90 DAC is an extremely

wide (full 90◦) conical opening on both sides of the cell. Awide opening angle is important for both powder and single-crystal angle-dispersive X-ray diffraction, since it increasesthe number of available Bragg diffraction peaks for a givenwavelength (photon energy). We chose a piston-cylinder de-sign for mechanical stability under high mechanical loads,as well as simplicity, reliability, and a possibility to increasepressure without micrometer measurements of possible incli-nations, which allows pressure adjusting without dismountingthe cell from a holder.

A resulting design is shown in Figure 1. To maximize thestability of the cell, a highest possible ratio of a piston heightover diameter is required with a maximum interface surface.This can be achieved by placing compression screws not in acylinder part (1 in Fig. 1), as is usually done, but inside a pis-ton part (2). Diamond anvils (4) are glued to the supportingseats (3), made either of tungsten carbide, or of cubic boronnitride, which is virtually transparent for high-energy X-rays,used in synchrotron-based X-ray diffraction studies. The sam-ple is placed in a small hole drilled inside a pre-indented metalgasket (5). A DAC loading force is produced by four screws(6): M4 in a metric version or #8-32 in imperial version ofthe cell. In order to make pressure control more smooth andaccurate, a pack of conical spring washers (7) is placed underthe screws. Without such spring washers, even a very small

angular rotation of a screw could produce significant pressurechange, which makes DAC operation much more difficult foran inexperienced user.

In the BX90 cell, there is no angular alignment of dia-mond anvils. According to our experience, the angular align-ment is not necessarily if supporting seats and a DAC body aremachined with high precision. On the other hand, mechanicalspherical or cylindrical “rocker” mechanisms are a source ofadditional instabilities, especially under high load. Positionalignment of diamond anvils is done with small alignmentsetscrews (8), four screws for each supporting plate. Safetysetscrew (9) should be finger tight inserted every time a DACneeds to be moved from place to place or stored for a longtime under pressure to prevent accidental pressure jump if acell is dropped. These screws also help in preserving and re-covering of one diamond anvil when another one broke duringan experiment.

The novelty of the BX90 design is not only in pressur-izing screws location, but also in four U-shaped cuts in thecylinder part of the cell (Fig. 1). These cuts along with 12-mmdiameter holes in the piston part give significant side access tothe inside of the cell. This side opening not only allows easyaccess to the anvil alignment screws, but also makes possibleto apply several experimental techniques that require mea-surements of a direct X-ray beam passed through an X-raytransparent (for example, beryllium) gasket: nuclear forwardscattering measurements or X-ray absorption measurement atlow energies. These openings also serve as wires passes—itis very easy to mount external resistive heaters, thermocou-ples, electrodes wires for resistivity measurements, etc., in-side the piston part and passing the wires though these sideholes. Afterwards, a DAC can be closed without interferingany of these wires, thanks to the U-cuts in the cylinder part.

When a miniature resistive heater is placed inside the cellfor high-temperature measurements, a significant temperaturegradient develops in the DAC body. As a result, a piston partexpands more than a cylinder part, and a cell might get stuck.In the BX90 DAC, however, the U-cuts give a cylinder partextra possibility for elastic response in such situation. Withthe miniature platinum resistive heater (Kantor et al.7, 10 inFig. 1), a stable heating for several hours up to 900 K (inan inert atmosphere) was performed at pressures exceeding100 GPa.

The outer diameter of the BX90 cell is 50 mm, which istypical for most of the diamond anvil cells and can be consid-ered as a standard diameter for major synchrotron facilities.This implies that BX90 can be used with most of existingDAC holders at major 3rd generation synchrotron sources.The cell length varies from 32 to 38 mm depending on thetype and thickness of supporting seats and diamond anvils.

Although BX90 is designed as a screw-driven cell, onecan use an external adapter to couple it with a gas membrane(Fig. 2, left). With increasing overall dimensions up to 59 (di-ameter) × 47.5 mm, one can take the full advantage of a gasmembrane DAC: remotely-controlled pressure regulation andisothermal compression or decompression either at low (in-side a cryostat), or high (using resistive or laser heating) tem-peratures. Since this gas membrane adapter leaves open ac-cess to the DAC screws, one can tighten the screws, remove

125102-3 Kantor et al. Rev. Sci. Instrum. 83, 125102 (2012)

FIG. 2. Left: a BX90 DAC (1) inside a gas-membrane adapter; ((2) cylin-drical vessel; (3) top cover; (4) gas membrane; (5) hardened steel pusher).Right: a compact (39 mm diameter and ∼28 mm height) version of BX90cell.

the adapter, and continue to use it as a mechanical DAC, storeand transport it easily at any moment and vice versa.

In a number of the high pressure experiments (on-linedouble side coaxial laser heating, low T measurements incryostat, optical measurements required short working dis-tance with high numerical aperture objectives, etc.), the avail-able space for high pressure vessel is limited. To fulfill suchapplications, we have developed a mini version (mBX90) ofthe BX90 with external diameter of only 39 mm and heightless than 30 mm (Fig. 2 right). There is no space for externalheater in the mBX90 but x-ray and optical access are the sameas for BX90. We have successfully tested this cell in the dou-ble side laser heating experiments when sample pressure, con-trolled by membrane, was changed in situ during laser heatingcoupled with on-line x-ray diffraction measurements in a widepressure-temperature range: 5–60 GPa and 1000–3000 K.

The BX90 cell can be machined with a standard tolerancefor small parts of about ±0.01 mm with the only exception fortwo polished cylindrical surfaces. After machining, each cellrequires individual adjustment for a tight contact between twoparts, which is done by gradual polishing and tryouts.

Several different alloys were tested as construction mate-rial for the cells: Inconel 718, Udimet 700, Republica, and Ni-monic. DACs (including backing plates) made of Inconel 718and Udimet 700 could be safely operated in air at temperatureup to 700 ◦C, and in an inert atmosphere (Ar + 2% H2) up to900 ◦C. Cells made of Republica alloy did not oxidize in airup to 750 ◦C, but the best performance was demonstrated bycells made of Nimonic–up to 850 ◦C in air, and up to 1100 ◦Cin an inert atmosphere. All the experimental results describedbelow were obtained from cells made of the Nimonic alloy.8

However, there is no reason to believe that BX-90 cannot bemade from beryllium bronze, for example, for low tempera-ture experiments or any other alloy typically used in this field.

The absence of “rockers” in the BX90 DAC might causesome difficulties when using the so-called Boehler-Almax de-sign anvils and supports, because they normally require angu-lar adjustment contrary to the standard anvils design. How-ever, this problem can be easily solved simply by aligningdiamond cullet parallel to the backing plate before applyingglue.

BX90 cells have been successfully used by several re-search groups: at the Bayerisches Geoinstitut (Bayreuth,

Germany), at GSECARS (Chicago, USA), at the Geophys-ical Laboratory of the Carnegie Institution of Washing-ton (USA), at the ESRF (Grenoble, France), and at GFZ(Geoforschungszentrum, Potsdam, Germany), and others. Anumber of experimental techniques have been combined sofar with the BX90 cell, including single-crystal and powderX-ray diffraction with external resistive and double-side laserheating; the Brillouin scattering and Raman spectroscopy;Mössbauer spectroscopy and nuclear forward scattering mea-surements; electrical resistivity measurements; infrared, opti-cal and X-ray absorption spectroscopies. Several examples ofsuch measurements are given below.

III. EXPERIMENTAL RESULTS

A. Brillouin scattering

The Brillouin scattering is an extremely powerful exper-imental technique that allows probing the acoustic phononsin material close to the gamma-point and thus determiningthe elastic (sound) waves velocities. If density of the sam-ple can be measured at the same time (for crystals, it can bemeasured via X-ray diffraction), the elastic constants of thematerial could be calculated. Elastic constants are of a greatimportance for solid state physics, as they not only determinea macroscopic strain response to an external stress, but alsoreflect the interatomic force constants in a material.

The Brillouin scattering setup at GSECARS, AdvancedPhoton Source, is described in detail elsewhere (Sinogeikinet al.6). Briefly, it operates in platelet geometry, where theincident laser beam enters the sample through one diamondanvil, and the scattered light is collected at the same exit anglethrough the second anvil. With this geometry, sound velocitiescan be measured directly without need to know the refractionindex of the measured material. In this geometry, higher scat-tering angle results in higher resolution, so it is important tohave large optical opening in a DAC.

The BX90 allows measurements in 80-degrees scatteringgeometry, which makes possible resolving of closely overlap-ping peaks. It is very important, because compressional wavevelocities in (quasi)-hydrostatic pressure media, such as he-lium or neon, are often very close to shear wave velocities inthe sample, and the same is true for shear velocities of dia-mond and compressional velocities in the sample. A typicalexample of such situation is shown in Figure 3, where Ne VP

is only ∼40 m/s faster than VS of a single-crystal ZnO sample.Therefore, highest possible resolution is often required in theBrillouin scattering experiments.

For practical reasons, it is important to know the po-sition of neon VP peak at a given pressure, because neonis one of the most used quasi-hydrostatic pressure media.Figure 4 shows the measured neon VP velocity as a functionof pressure at room temperature. These measurements havebeen performed at the GSECARS Brillouin setup at beamline13-BMD at APS. Diamond anvils with 400 μm culets wereused, and neon was loaded using a COMPRESS/GSECARSgas loading system (Rivers et al.9) as a pressure medium.A sample studied was a double-polished ZnO single-crystal;the ZnO results will be published elsewhere. Pressure was

125102-4 Kantor et al. Rev. Sci. Instrum. 83, 125102 (2012)

Velocity (m/s)

-12000 -9000 -6000 -3000 0 3000 6000 9000 120000

10

20

30

40C

ount

s ZnO

Vs

Ne

Vp

ZnO

Vp

Ne

Vp

BS

Dia

mon

dV

s

Ray

leig

hpe

ak

FIG. 3. Brillouin scattering spectrum of the ZnO single crystal in neon pres-sure medium at 4.1 GPa. Both Stokes and anti-Stokes parts of the spectrumare shown. Peaks are marked in the figure; “BS” stands for back-scattered.Elastic Rayleigh peak is several orders of magnitude stronger than the sam-ple peaks.

determined using X-ray diffraction from a small piece of goldplaced inside of the sample chamber (Fei et al.10). As seenfrom Fig. 3, our results are in good agreement with early ul-trasonic measurements in a gas vessel to 1 GPa (Kortbeeket al.11). It is clearly seen that above the solidification pressureabout 4.7 GPa (Vos et al.12), sound velocities discontinuouslyincrease along with the data points scattering. The latter is ex-plained by the fact that crystalline neon is no longer elasticallyisotropic, and the effective measured velocity is an average ofVp in several crystallites of a different orientation.

There is no fundamental theory of an equation of stateof liquid, therefore no simple analytical form for the Vp(P)dependence is available. We fitted a simple power equation tothe experimental data below 4.7 GPa (solid line in Fig. 4), andthe fit gives Vp[m/s] = 1717.83 × P[GPa]0.4054. This equation

Pressure (GPa)

0 2 4 6 8 100

1000

2000

3000

4000

5000

present studyKortbeek et al., 1988Power fit

Vel

ocity

(m/s

)

FIG. 4. Compressional waves velocity in neon as a function of pressure. Dia-monds: present study, crosses: data from Kortbeek et al.10 Solid line: a powerfit to the fluid phase of neon (for P < 4.7 GPa), see text. Error bars are smallerthan symbol size.

5 mm

35°

5 mm

57°

5 mm

90°

FIG. 5. Geometry of different types of diamond anvils and supporting seatsand corresponding X-ray and optical openings in the BX90 cell. Top: a typ-ical setup for optical measurements: standard diamond anvils of ∼2.1 mmthick and a tungsten carbide supporting plate of 3.2 mm thick. Due to thehigh refraction index of diamond, a full 90◦ optical opening is achieved (bolddashed line), while the X-ray opening is only 35◦. Center: a typical setup forpowder X-ray diffraction studies. A standard diamond anvil of 2.1 mm and a5 mm thick cubic boron nitride supporting plate provide a 57◦ X-ray opening.Bottom: a highest possible X-ray opening can be achieved using specially de-signed anvils and supporting plate (Boehler and De Hantsetters12).

can predict, with a reasonable enough precision, the positionof a liquid neon Brillouin scattering peak at a given pressure.

B. X-ray diffraction

As mentioned above, the high axial opening angle ofthe BX90 cell is also valuable for an angle-dispersive X-raysdiffraction. However, in most cases an X-rays opening an-gle is limited not only by a diamond anvil cell, but also bya supporting plate for a diamond anvil. In Figure 5, the mostcommon combinations of the diamond anvils and supportingplates are shown.

Due to the extremely high refractive index of diamond,an optical beam entering diamond at the angle of incidenceof 45◦ travels inside the anvil at the angle of refraction ofjust 17◦ (Fig. 5 top, bold dashed line). Therefore, a full 90◦

125102-5 Kantor et al. Rev. Sci. Instrum. 83, 125102 (2012)

FIG. 6. A reconstructed unwrapped image of the (h k 10) reciprocal spacesection of Cr2O3 crystal at 70 GPa. Ten X-ray diffraction peaks are labeled,and reciprocal lattice vectors a* and b* are shown.

optical opening can be easily achieved with a standard bril-liant cut diamond anvils of about 2–2.2 mm thickness andthe relatively thin (3.2 mm) tungsten carbide supporting seats.The X-rays opening in this case is limited to only ∼35◦, whichis, however, enough for phase determination and the latticeparameters refinement in most cases when a synchrotron ra-diation source (typically λ = 0.3–0.4 Å) is used. For powderdiffraction combined with the laser-heating, more suitable isthe use of X-ray-transparent supporting plates, such as thosemade of 5-mm thick cubic boron nitride (Fig. 5, center). Inthis combination, an X-ray opening of ∼57◦ is sufficient forall kinds of X-ray diffraction structural studies: investigationsof equations of state and phase transitions, chemical reactions,and melting phenomena, etc.

A full use of the 90◦ opening of the BX90 cell withthe X-ray diffraction can be made with the help of so-calledBoehler-Almax anvils (Fig. 5, bottom). These anvils withconical supports and matching carbide seats can give a full90◦ opening in 4θ (Boehler and De Hantsetters13). Such abroad X-ray opening is important for the single-crystal X-raydiffraction, when a cell has to be rotated around its axis in or-der to bring as much diffraction planes as possible in Bragg’sposition.

Figure 6 shows a reconstructed unwrapped image of the(hk10

)section of the reciprocal space of an α-Cr2O3 single

crystal, collected at 70.4(5) GPa in the BX90 cell. These mea-surements were performed at ID09A at the European Syn-chrotron Radiation Facility (ESRF) using a monochromaticX-ray beam (λ = 0.4148 Å) and a MAR555 flat panel detectormounted at about 310 mm apart from the sample. A syntheticCr2O3 single crystal of 30 × 30 × 15 μm3 was loaded in a100 μm hole of an indented rhenium gasket along with severalruby spheres for quick pressure determination (Mao et al.,14

1986). Neon was loaded into the sample chamber at 1.4 kbargas pressure, and used as a pressure transmitting medium andas an internal pressure standard (Fei et al.10). At each pres-sure points, 160 independent frames in the ω-scanning rangeof −40◦ to +40◦ were collected (0.5◦ scanning step size) withan exposure time of one second. The X-ray beam size was

about 10 × 10 μm2 FWHM. The detailed results of this high-pressure study are published elsewhere.15

As seen from Fig. 6, only for one particular section 10 in-dividual reflections were recorded and overall 408 reflectionswere observed, among which 63 were unique. Such a widecoverage of the reciprocal space allows a very accurate re-finement of the crystal structure parameters with the resultingR1 factor of 4.9% at pressure exceeding 70 GPa.

C. Resistivity measurement

Electrical resistance is one of the most useful proper-ties of materials for studies of many pressure-induced effectsconnected to alterations of atomic or molecular interactionsin solids. Different examples of pressure-induced phenom-ena such as metallization, superconductivity, delocalization ofelectrons have been successfully studied using transport prop-erty measurements in diamond anvil cells.

In geophysics and in planetary sciences, electrical con-ductivity measurements are essential in order to understandelectromagnetic phenomena within planetary bodies. Impor-tant constrains in the mineralogical composition of the innerEarth can be obtain using such measurements (Katsura et al.16

and Ohta et al.17). However, technically such measurementsare still difficult and information about electrical properties ofeven major Earth’s lower mantle phases (ferropericalse andFe, Al-bearing magnesium-silicate perovskite) as functionsof pressure, temperature, and compositions is quite limited.Novel BX90 diamond anvil cell, as pointed above, simplifiesthe preparation of the setup for resistivity measurements inDAC and, due to large optical opening, makes it easier to cou-ple them with laser heating.

In order to illustrate the application of BX90 for the re-sistance measurements at high temperatures and pressures,we studied (Mg0.60Fe0.40)(Si0.63Al0.37)O3 silicate perovskitesynthesized in a multi-anvil press (see Dubrovinsky et al.18).Methodology of a sample preparation, measurements, andlaser-heating set-ups has been described in our previous

Pressure (GPa)10 30 50 70 90

2

3

4

5

6

7

1250(50) K1800(50) K2300(100) K

logR

(Ohm

)

FIG. 7. Resistivity of a synthetic (Mg0.60Fe0.40)(Si0.63Al0.37)O3 silicate per-ovskite, measured at 1250(50) K (black circles), as 1800(50) K (open trian-gles) and at 2300(100) K (gray diamonds), using a laser heated BX90 cell.

125102-6 Kantor et al. Rev. Sci. Instrum. 83, 125102 (2012)

publications (Kuznetsov et al.19 and Dubrovinsky et al.20).The BX90 cell combines large side-opening with high me-chanical stability usual for piston-cylinder devices. In themulti-pin type DACs often used for resistivity measurements,it is not so easy to maintain stable and precise aliment atmegabar pressure range, especially at high temperatures. In-deed, Figure 7 shows that an accurate data on resistanceof a silicate perovskite may be collected at pressures above80 GPa and temperature of 1800(100) K.

IV. CONCLUSIONS

A new design of a BX90 diamond anvil cell is presented.The cell’s features are a wide (90◦) symmetrical axial open-ing, useful 12-mm side openings, and a vast stability providedin combination with moderate external dimensions (50 mmdiameter and ∼35 mm thickness). All these features make theBX90 cell applicable to a wide range of experimental tech-niques. Examples of investigations using the Brillouin scatter-ing, single-crystal X-ray diffraction, and the resistivity mea-surements in BX90 are given.

ACKNOWLEDGMENTS

Authors would like to acknowledge M. Hanfland and M.Merlini for their assistance with the X-ray diffraction mea-surements and data treatment. The work was supported bythe German Research Foundation (DFG) through the DFGPriority Program 1236. N.D. thanks the DFG for financialsupport through the Heisenberg Program. GeoSoilEnviro-CARS is supported by the National Science Foundation–

Earth Sciences (EAR-1128799) and Department of Energy–Geosciences (DE-FG02-94ER14466).

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