Prospects of using synchrotron radiation facilities with diamond-anvil cells: High-pressure research applications in geophysics

Nuclear Instruments and Methods 177 (1980) 219-226 © North-Holland Publishing Company

PROSPECTS OF USING SYNCHROTRON RADIATION FACILITIES WITH DIAMOND-ANVIL CELLS: HIGH-PRESSURE RESEARCH APPLICATIONS IN GEOPHYSICS M.H. MANGHNANI, L.C. MING Hawaii Institute of Geophysics, University of Hawaii, Honolulu, Hawaii, 96822, USA and J.C. JAMIESON Department of Geophysical Sciences, University of Chicago, Chicagolllinois 60637, USA

Diamond-anvil pressure cells have proven versatile and useful for conducting high pressure research in the submegabar range. The interfacing of diamond-anvil cell technology with synchrotron facilities seems a logical new step for carrying out in situ X-ray diffraction studies of materials under extreme conditions of combined high pressure and temperature. The conventional film method of X-ray diffraction has definite limitations which call for the energy dispersive analysis techniques. Various potential high pressure-temperature studies in geophysics and related fields involving the use of diamond-anvil cell, synchrotron facilities and energy dispersive techniques are exemplified. For geophysical studies the conditions prevailing in 86% of the Earth's volume are capable of being simulated completely in pressure, and partially in pressure and temperature, simultaneously.

trum, well-defined polarization and highly collimated beam will certainly obliviate these difficulties. The interfacing of diamond-anvil cell technology with synchrotron radiation facilities seems a logical new step in X-ray diffraction studies of materials in the extreme environments of combined high pressures and high temperatures. No such combined studies have yet been reported. Indeed, the feasibility of such an application has already been demonstrated by Buras et al. [ 4 - 6 ] at Deutsches Elektronen-Synchrotron (DESY) and by Bordas et al. [7] at Synchrotron Radiation Facility at Daresbury Laboratory, England (NINA). The purpose of this note is to review the potential applications of diamond-anvil cell technology adapted with synchrotron facilities in research in geophysics and related fields.

1. Introduction Diamond-anvil pressure cells are currently the best pressure vessels for submegabar high pressure research utilizing optical, X-ray and other techniques for diagnosis of physical property changes and phase transitions in materials. They have also been used [1] for investigating melting relations in iron under simultaneously high pressures and high temperatures. At ambient temperature, experiments are routinely conducted at several hundred kbar; a pressure of 1.72 Mbar has been recently sustained [2]. Under pressures of a few llundred kbar, temperatures of up to 1800°C have been attained by resistance heating [ 1] and up to 3000°C by high power lasers [3]. The main disadvantages of using diamond-anvil cells in conjunction with common "film method" X-ray diffraction on powder samples are the long exposure times ( 1 0 0 - 3 0 0 h) required because of adsorption by diamond anvils, and small sample size. These limitations preclude their full use in diffraction analysis of materials undergoing time-dependent phenomena, such as rapid transformation of metastable phase, as well as in studies needing a multitude of data points such as phase diagram as a function of pressure, temperature and composition. Synchrotron radiation with several unique features such as high intensity smooth spec-

2. Diamond-anvil cells for high pressure research The diamond-anvil pressure cell is a powerful tool for investigating various physical properties (i.e., lattice parameters [8], equation of state [9], phase transformations [10], single crystal structure [11], electrical resistivity [12], viscosity [13], optical absorption [14], infrared and Raman spectroscopy 219

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[15], M6ssbauer spectroscopy [16], and Brillouin scattering [17]) under extremely high pressures. It has been well calibrated at room temperature using the Ruby fluorescence (R-line) method [18] although at other temperatures the calibration is still under study. As stated earlier its main disadvantage in X-ray diffraction studies lies in the long exposure time ( 1 0 0 - 3 0 0 h) required. Two types of diamond cells now commonly used are illustrated in fig. 1 (after Bassett and Ming [19], and Mao and Bell [20]). Both of these cells can be readily adapted to synchrotron radiation. They are small (10 cm X 25 cm X 10 cm), portable ( 1 - 5 kg),

and require minuscule samples (mg). The ceils can be mounted while retaining a given pressure indefinitely. A distinct safety advantage is that the adjustments, loading and pressure measurements can all be carried out away from the radiation source. Another advantage is that, as compared with the cost of other high pressure apparati such as polyhedral-anvil presses, they are relatively inexpensive (cost is about $ 7500). For X-ray diffraction studies ordinary "commercial" diamonds may be obtained in desired anvil form for (currently) less than $ 750 a pair. Unless used for ultra-high pressure work (>400 kbar) they will last more or less indefinitely.

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3. Interfacing diamond-anvil pressure cell with X-ray energy dispersive analysis system and/or synchrotron radiation

(b) Fe at ambient pressure, (c) Mn at elevated temperature, 1 atm; followed by phase change (a - fl), (d) TeO2, room temperature, to 80 kbar, (e) FeS, lattice parameters to 70 kbar. The latter two studies successfully used a diamond cell for generation of high pressure. In fig. 3 we show their 80 kbar diffraction pattern of TeO2 taken in 2000 s (½ h). In addition to the Buras group at DESY, Bordas et al. [7] have obtained X-ray diffraction patterns on Si, NaC1 and KC1 under ambient conditions at NINA (Daresbury). The combination of a diamond-anvil cell with its pressure and temperature potentialities (1 Mbar and ~>1000°C, respectively) with synchrotron radiation in the X-ray regions (1-7 keV), and energy dispersive detection is therefore an extremely potent tool not only for geophysics studies but also in research fields covering metallurgy, solid state chemistry, physics and material sciences.

The advantages of rapid analysis of the data by energy-dispersive (ED) X-ray diffractometry over the routine monochromatic X-ray diffractometry are becoming very apparent to investigators who study materials under extreme environmental conditions. In research involving diamond-anvil pressure cell, we fmd a constant beam-sample angle desirable due to geometrical constraints. The coupling of energy-dispersive techniques with high-pressure technology has been performed by Albritton and Margrave [21], Mahajan et al. [22], and Skelton et al. [23] (fig. 2). Ordinary X-ray generators have been used in such studies, but disadvantages are: (1) comparatively low intensity requiring several hours of exposure time (this is also true to some lesser extent when a highintensity rotary-anode type of X-ray generator is used); (2) practically unknown polarization which complicates ED data analysis: and (3) characteristic radiation superimposed on the needed continuum. Combined use of synchrotron radiation, as the source of X-rays, and energy-dispersive X-ray diffraction techniques avoids these difficulties and cuts down the exposure time drastically as demonstrated by Buras et al. at DESY in several recent studies on the following crystalline solids: (a) Si powder and single crystal at ambient condition,

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4. Research applications in geophysics 4.1. General background

The Earth (and all other planetary objects) may be regarded as a natural high pressure, high temperature laboratory. Most of the information about the Earth's interior structure and composition has been inferred from seismic, gravity, thermal, electrical and electro-

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On the basis of the seismic data the Earth has been divided into three distinct regions: crust ( 0 - 3 0 km), mantle (30-2886 km) and core (2886-6371 km). The Earth's mantle consisting mainly of constituents SiO2, MgO, FeO, A1203 and CaO, is subdivided into the upper mantle (30-400 km), transition zone (400-1000 km) and lower mantle (1000-2886 km) (fig. 4). The core is divided into an outer liquid core (2886-5160 km) consisting mainly of F e - N i alloy with 10-15% Si or S, and an inner solid core (5160-

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Table 1 Pressure, density and estimated temperature at various depths in the Earth from BuUen [24] Depth (km)

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6371 km) consisting mainly of F e - N i alloy. The transition zone in the mantle, characterized by three abrupt increases in longitudinal and shear wave seismic velocities (Fp and Vs) at about 400, 570 and 650 km, is considered to be a result of high pressure transformations in ferromagnesian silicates such as (Mg, Fe)2SiO4 (olivines), (Mg,Fe)SiO3 (pyroxenes)and (Fe,Mg)aA12SiaOn (garnets), and solid solutions involving pyroxenes and A1203 [25]. 4.2. High pressure-temperature phase transformations in the Earth's Interior Geophysicists and geochemists are continually striving to unravel possible mineralogical composi-

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tions and phases in the Earth's interior. The problem has been partially answered by high-pressure (up to 400 kbar), high-temperature (up to 2000°C) phase transformation studies on ferromagnesian silicates using the diamond-anvil pressure cell coupled with a YAG heating system [ 10]. Even in a simple system like MgO-SiO2, multiple phase transitions and reactions are involved (fig. 5) [10]. Further complexities of the chemical reactions, disproportionation, and phase changes in the Earth's interior can be appreciated from fig. 6, where additional components and solid solutions are introduced. The figure illustrates sharp increases in densities of successive high-pressure phases with increasing pressure (depth) in the systems (Mg, Fe)SiOa • A12Oa and (Mg, Fe)2SiO4, separately and in combination [10]. The interpreted density jumps at depth of about 400 and 650 km correlate well with the observed seismic discontinuities at these depths [26]. Because of the large uncertainties in pressure calibration at high temperatures, the results of phase transformation studie¢of the Earth's materials can, at present, only be used" qualitatively. Furthermore, in these studies the high pressure phases formed have been identified by X-ray diffraction on quenched and unloaded samples under ambient conditions, and it is possible that some stable high-pressure phases were missed during the quenching and unloading processes, and metastable phases were formed instead. Because of speed of data collection (about 30 min) in using synchrotron radiation, there is less possibility of reactivity of diamond anvils with the sample at extremely high temperatures. Also, temperatures which are difficult to control for long periods (100-300 h) of study with ordinary X-ray sources (1 kW) may now be sufficiently under control for a 30 min study. A less obvious but still very important application is the V. EXPERIMENTALTECHNIQUES

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collection o f pressure t e m p e r a t u r e - c o m p o s i t i o n ( P T - X ) data for a geochemical system. A reasonably comprehensive in situ study of phase occurence at (P, T) points might require 10 compositions (X) at 10 pressures and 10 temperatures. For I00 h exposures (for phase detection only), this is eleven years for one camera. Multiple cameras would shorten this time by a factor of ten leaving still a mind-boggling task. (For those who are masochistically inclined, contemplate a ternary system at P, T!) The 30 min synchrotron exposures would permit the 103 point study to be performed over a month. In practice a 100 point survey could be used to ascertain areas of P, T, X diagram which were worth more detailed study. Interfacing diamond-anvil pressure cell with energy dispersive system and the synchrotron radiation will, therefore, make in situ studies under simultaneous high pressure-high temperature environments much more feasible. Results o f such experiments will be of great value in unambiguous identification of the high pressure-high temperature phases in the Earth's deep interior, as well as provide reliable data on the pressure and temperature conditions under which each of the phases is formed. The seismic velocities in the Earth's interior can then be interpreted more quanti-

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M.H. Manghnani et al. / High-pressure research application tatively in terms of composition and phases present. It would be also possible to establish reliable P - T - X phase diagrams from which important thermodynamic parameters such as dT/dP, AS, and AH can be extracted to shed light on the nature of the mantle dynamics. The other potential geophysical uses of diamondanvil pressure cell interfaced with synchrotron and energy-dispersive facilities are: (1) kinetics of phase transitions at high pressures and temperatures. (2) Time-dependent metastable reactions and phase transitions. (3) Equation of state of the Earth's materials. (4) Thermal expansion at higher pressures and temperatures. (5) Structural refinement of new high pressuretemperature phases. (6) Melting relationships of silicates, oxides and F e - N i alloys at high pressures. (7) Strength and strain measurements. All of the above applications of diamond-anvil pressure cell interfaced with synchrotron and energydispersive facilities also have potential applications in solid state physics, chemistry, metallurgy and matedals sciences. Besides these applications, there are a number of other studies such as EXAFS [27] (Ingalls and Shimomura and co-workers), that have been successfully carried out with diamond anvil. The other areas of synchrotron research with diamond-anvil that hold promise are: X-ray fluorescence and emission spectroscopy of materials under high pressure and high temperature. This research was supported by Department of Energy contract EY-76-S-03-0235 (P.A. 1 2 ) a n d National Science Foundation grants EAR 76-23362 (University of Hawaii) and EAR 76-81503 (University of Chicago). Thanks are due to Earl F. Skelton and Peter M. Bell for reviewing the manuscript and to Rita Pujalet for helpful editorial comments (Hawaii Institute of Geophysics contribution no. 1063).

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[5] B. Buras, J.S. Olsen and L. Gerward, Nucl. Instr. and Meth. 132 (1976) 193. [6] B. Buras, N. Nimura and J.S. Olsen, J. Appl. Cryst. I1 (1978) 137. [7] J. Bordas, A.M. Glazer, C.J. Howard and A.J. BourdilIon, Philos. Mag. 34 (1977) 35. [8] H.K. Mao, T. Takahashi, W.A. Bassett and J.S. Weaver, J. Geophys. Res. 74(4) (1969) 1061; D.R. Wilburn and W.A. Bassett, High Temp.-High Press. 9 (1976) 343; D.R. Wilburn and W.A. Bassett, Am. Miner. 63 (1978) 591; L.C. Ming and M.H. Mangt~nani, J. Appl. Phys. 49(1) (1978) 208. [9] H.K. Mao and P.M. Bell, J. Geophys. Res. 84(B9) (1979) 4533; J.S. Weaver, T. Takahashi and W.A. Bassett, in: Accurate Characterization of the High Pressure Environment, ed., E. Lloyd (1971) p. 189. [10] L.G. Liu, Phys. Earth Planet. Int. 19 (1979) 319; L.G. Liu in: The Earth: Its Origin, Structure and Evolution, ed., M.W. McElhinny (Academic, London, 1980) 177; H.K. Mao and P.M. Bell, in: Energetics of Geological Processes, eds., S.K. Saxena and S. Bhattacharji (1977) p. 237; L.C. Ming and W.A. Bassett, Science 187 (1975) 66; L.C. Ming and M.H. Manghnani, Geophys. Res. Lett. 6(1) (1979) 13; L.G. Liu, Earth Planet. Sci. Lett. 42 (1979) 202. [111 L. Merrill and W.A. Bassett, Rev. Sci. Instr. 45 (1974) 209; R.M. Hazen, Am. Miner. 61 (1977) 266; L.W. Finger and H. King, Am. Miner. 63 (1978) 337; L. Levien, C.T. Prewitt and D.J. Weidner, Am. Miner. 64 (1979) 84. [121 H.K. Mao, Carnegie Inst. Washington Yr. Book (72) (1973) 554; H.K. Mao and P.M. Bell, in: High Pressure Research Applications in Geophysics, eds., M.H. Manghnani and S. Akimoto (Academic Press, New York, 1977) p. 493; S. Block, R.A. Forman and G.J. Piermarini, in: High Pressure Research Applications in Geophysics, eds., M.H. Manghnani and S. Akimoto (Academic Press, New York, 1977) p. 503,A.W. Webb, D.U. Gubser and L.C. Towle, Rev. Sci. Instr. 47 (1976) 59. [131 G.J. Plermarini, R.A. Forman and S. Block, in: HighPressure Science and Technology, eds., K.D. Timerhaus and M.S. Barber (Plenum Press, New York, 1979) p. 860. [14] H.K. Mao and P.M. Bell, Carnegie Inst. Washington Yr. Book 71 (1972) p. 520; H.K. Mao and P.M. Bell, Geochim. Cosmochim. 39 (1975) 865; R.M. Abu-eid, in: The Physics and Chemistry of Minerals and Rocks, ed., R.G.J. Strens (John Wiley and Sons, New York, 1976) p. 641. [15] R. Farroro and L.J. Basile, Appl. Spectrosc. 28 (1974) 505; J.F. Mammone and S.K. Sharma, Carnegie Inst. Washington Yr. Book 79 (1980). [16] F.E. Higgins, H.K. Mao and D. Vlrgo, Carnegie Inst. Washington Yr. Book 75 (1976) 405; H.K. Mao, D. Virgo and P.M. Bell, Carnegie Inst. Washington Yr. Book 76 (1977) 522. [17] C.H. Whitefield, E.M. Brody and W.A. Bassett, Rev. Sci. Instr. 47 (1976) 942; W.A. Bassett, D.R. Wilburn, J.A. Hrubec and E.M. Brody, in: High-Pressure Science and Technology, Vol. 2, eds., K.D. Timmerhaus and M.S. Barber (Plenum Press, New York, 1979) p. 75. V. EXPERIMENTALTECHNIQUES

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[18] G.J. Piermarini, S. Block, D.J. Barnett and R.A. Forman, J. Appl. Phys. 46 (1975) 2774; H.K. Mao, P.M. Bell, J.W. Shaner and D.J. Steinberg, J. Appl. Phys. 49 (1978) 3276; H.K. Mao, P.M. Bell, K.J. Dunn, R.M. Chenko and R.C. deVries, Rev. Sci. Instr. 50(8) (1979) 1002. [19] W.A. Bassett and L.C. Ming, in: The Physics and Chemistry of Minerals and Rocks, ed., R.G. Strens (1977) p. 366. [20] H.K. Mao and P.M. Bell, Ann. Rept. Director Geophys. Lab. 74 (1975) 402. [21 ] L. Albritton and J.L. Margrave, High Temp.-High Press. 7 (1975) 325. [22] V.K. Mahajan, P.T. Chang and J.L. Margrave, High Temp.-High Press. 7 (1974) 325.

[23] E.F. Skelton, C.Y. Liu and I.L. Spain, High Temp.High Press. 9 (1977) 19. [24] K.E. Bullen, The Earth's Density. (John Wiley, New York, 1975). [25] A.E. Ringwood, Composition and Petrology of the Earth's Mantle (McGraw-Hill, New York, 1975). [26] D.L. Anderson, Ann. Rev. Earth Planet. Sci. 5 (1977) 179. [27] R. Ingalls, G.A. Garcia and E.A. Stern, Phys. Rev. Lett. 40 (1978) 334; R. Ingalls, J.E. Whitmore, J.M. Granquada and E.C. Crozier, Proc. 7th AIRAPT Conf., Le Creusot, France, 1979, to be published; R. Ingalls, E.D. Crozier, J.E. Whitemore, A.J. Seary and T.M. Tranquada, to be published in J. Appl. Phys.; O. Shimomura, T. Fukamachi, T. Kawamura, S. Hosoya and A. Bienenstock, Jap, J. Appl. 17 Suppl. 17-2 (1978) 221.