Pressure In Diamond Anvil Cell Research Articles

Single crystal study of sodalite at high pressure

Abstract X-ray single crystal structure determinations of sodalite (Na8[Al6Si6O24]Cl2, cubic, P[unk]3n) were performed under high hydrostatic pressure in diamond anvil cells. Natural (from Bancroft/Canada) and synthetic specimens were investigated. The continuous decrease of the lattice constant with increasing pressure indicates that there are no first order phase transitions in the pressure range investigated. However, the comparison of the results with data obtained from previous experiments and on related structures of tugtupite and helvite, reveals a possible change in the compression mechanism or a phase transition at about 3 GPa. The compression mechanism operates on the intertetrahedral bonding parameters of the alumino-silicate framework structure. The volume reduction is mainly achieved by the deformation of bonding angles between the different TO4-tetrahedra. As a result, the size of the β-cages and consequently the size of the [Na4Cl]3+-clusters decreases. A pressure induced amorphization of the crystal structure was detected at 7.3 GPa. Experiments on the synthetic samples were done to prove this low value of pressure induced amorphization. On lowering the pressure, recrystallization from the amorphous phase occured at 5.8 GPa.

Studies of irradiated cadmium sulfide in a diamond anvil pressure cell

Cadmium sulfide (CdS) was irradiated with 7 MeV electrons in the fluence range 1013–1017 cm−2. The samples were subsequently studied in a diamond anvil cell up to a pressure of 100 kbar (1 bar = 105 Pa). Samples irradiated up to 1015 cm−2 underwent the wurtzite (yellow) to rock-salt (black) change of phase at 27 ± 2 kbar. Samples irradiated at 1016, 3 × 1016, and 1017 cm−2 also underwent the wurtzite to rock-salt transformation at 27 ± 2 kbar, but at the critical pressure they changed to an orange form which colour persisted as the pressure was increased. As the pressure was decreased, the orange samples reverted to the rock-salt structure at 30 ± 2 kbar, and then to the orange form, which persisted to atmospheric pressure. Heating the recovered orange CdS to 500 ± 50 °C returned it to its wurtzite form. X-ray diffraction studies of the irradiated but not pressurized samples revealed two peaks that correspond to the distance between planes (d) of 1.40 and 1.26 Å (1 Å = 10−10 m). In the irradiated and pressurized samples, we observed peaks having d = 1.47, 1.40, 1.32, 1.27, 1.19, 1.16, 1.09, and 0.96 Å. We attribute the orange form of CdS to defects. Irradiation of CdS with 7 MeV electrons to a fluence of 1016 cm−2 tends to suppress the wurtzite to rock-salt change of phase.

Reversed brackets for the P1 <--> I1 transition in anorthite at high pressures and temperatures

The pT to IT phase transition in end-member anorthite, CaA12Si20g, has been reversed in-situ at high pressures and temperatures in an internally heated diamond-anvil pressure cell using single-crystal X-ray diffraction. The unit-cell parameters of anorthite were determined at 48 temperature-pressure points up to 255 OCand 2.6 GPa. At high pressures and temperatures, from room temperature up to -225°C, the transition is marked by a first-order step in the unit-cell volume and the complete disappearance of c and d reflections from the diffraction pattern. From room temperature to -195 °C and 2.1 GPa, the transition boundary is linear and nearly isobaric, with a slope, dP/ dT, of -0.003 GPa/°C. From 195 to 240°C and 1.5 GPa the boundary is curved, with increasingly negative dP/dT, and the magnitudes of 11V and the scalar strain associated with the transition decrease to about 75% of their high-pressure values of -0.2 and -0.011 %. From 1.5 GPa to room pressure, the boundary is isothermal at 240°C and is marked by the disappearance of the c and d reflections, although there are no detectable discontinuities in the unit-cell parameters. The phase transition remains unquenchable over the entire boundary. The distinct changes in character of the phase transition and the trajectory of the equilibrium boundary in P-T space are associated with a crossover in the IT phase field that is marked by a sudden change in cell parameters of this phase over the pressure interval of -1.5-2.0 GPa.

圧力誘起非晶質相転移機構

In the last decade the pressure-induced amorphization of several crystals such as SiO2, Ca (OH) 2, H2O, GeO2, α-AlPO4 etc. have been found under compression at room temperature. The pressure-induced amorphization was previously regarded as the thermodynamically metastable phase, which corresponds the super cooled liquid phase at room temperature. The amorphization is a precursor phenomenon of the phase transition to the high pressure form. There are two different types of the reversible and irreversible amorphization. Dynamical lattice-instability due to shear and stress induces the reversible amorphization, which produces memory glass. On the other hand the irreversible mode is attributed to the nucleation of highpressure form in the parent lattice but thermal energy is not high enough to provide the large crystallite size coherent to the X-ray wave length. The successive structure change of the pressure-induced amorphizaiton was investigated under various pressure and temperature by X-ray diffraction study, XAFS and Raman spectroscopy with diamond anvil pressure cell.

A high-pressure study of thallium

High-pressure experiments on metallic thallium have been carried out using a diamond-anvil cell for pressures up to 32 GPa. A hexagonal close packed → face-centred cubic (f.c.c.) phase change takes place around 4 GPa. Fitting of the experimental data to the Murnaghan and Birch equations of state has been used to obtain values for the bulk moduli and their pressure derivatives for the two phases. Extrapolation of the high-pressure data for the f.c.c. phase to low pressure has been used to obtain an estimate of the pressure to about 0.23 GPa in nanosized metastable f.c.c. thallium inclusions formed in aluminium by ion implantation.

High-Pressure Powder Diffraction on Synchrotron Sources

The sample volume in diamond-anvil pressure cells suitable for X-ray powder diffraction studies is very small (</= 100 mum across). The resulting low signal-to-noise ratio has made it very difficult to obtain useful results with monochromatic angle-dispersive techniques, and the alternative white- beam energy-dispersive techniques have limited resolution and generally give unreliable peak intensities. The situation has been transformed recently by the introduction of the image-plate two-dimensional detector, which allows angle-dispersive methods to be used with a greatly increased signal and improved powder averaging. A short review is given of this development, the experimental techniques, and the principal advantages, particularly as found in results obtained at SRS Daresbury over the past two or three years.

Synchrotron X-Ray Powder Diffraction Facilities at Daresbury Laboratory

A review, with 26 refs. There are three exptl. stations dedicated to powder diffraction on the UK Synchrotron Radiation Source at the SERC Daresbury Lab. Station 2.3 houses a two-circle angle-dispersive (monochromatic) powder diffractometer, based on the Hart-Parrish design, and is sited on a 1.2 T dipole bending magnet source. This diffractometer can be used to collect data on specimens in the temp. range 10-300K. Station 9.1, which also houses a two-circle angle-dispersive powder diffractometer, is sited on a 5T wiggler magnet source and can be used in high and low resoln. modes. This diffractometer can be used to collect data on specimens in the temp. range 15-1200K and at high pressures. It is also possible to collect data for in situ chem. reaction studies. Station 9.7 houses an energy-dispersive (white beam) diffractometer, and is also sited on a 5T wiggler magnet source. The very high synchrotron radiation flux from the white beam means that it is possible to carry out diffraction expts. on very small samples (e.g. samples under pressure in diamond anvil cells), or to collect time-resolved powder diffraction data (e.g. kinetic studies). Two new stations are currently under construction and will be commissioned during 1994. [on SciFinder(R)]

圧力誘起非晶質相転移の地球科学的意義

In order to elucidate many geophysical problems induced from the global techtonics, dynamics of the mass transfer has attracted an interest. In association with the seismic researchs, material transformations, such as transition, decomposition, recrystallization, melting, etc. have been also greatly intrested under the conditions of heating, compression and stress field. Pressure-induced amorphizations of many minerals such as quartz, cristobalite, tridymite, anorthite, serpentine, fayalite and several other hydrates have been reported. These amorphizations and shear-instability will play a role to conduct the transformational ductile flow in the subduction zone, which would be the origin of the deep earthquake. Several different types of the pressure-induced amorphization were proved by the X-ray diffraction studies under high pressure and heating condition using multianvil high-pressure appararus and diamond anvil pressure cell. If the amorphization is the quenchable case, the pressure-quenched amorphous substance was examined by electron microscope, Raman spectrosope, EXAFS together with X-ray diffraction study.

Single-crystal X-ray diffraction at high pressures with diamond-anvil cells

Abstract The past twenty years have seen the widespread development of diamond-anvil pressure cells (DAC's) suitable for carrying out single-crystal X-ray diffraction experiments to pressures in excess of 10 GPa. The relative advantages and disadvantages of the various types of DAC are discussed and the basic techniques for their operation, including pressure measurement and the collection of diffraction data, are described. The application of DAC's to the study of structural phase transitions at high pressures is also reviewed.

Kinetic study of the GeO2 transition under high pressures using synchrotron X-radiation

An in situ observation of the structure transition of GeO2 has been made under 3.0 GPa at various temperatures with a diamond-anvil pressure cell. The time-resolved energy-dispersive (ED) diffraction experiment was undertaken using synchrotron X-radiation. A profile analysis of ED spectra observed every 15 min elucidates the transition process from the α-quartz form (P3221, Z = 3) to the rutile form (P42/mmm, Z = 2). The time-resolved measurement of their diffraction intensity ratio reveals the change of the mass fraction of the transformed product with time, which provides the transition rate. A transition curve showed three stages at low temperature; firstly a long inductance period after initiation of heat supply, secondly a rapid initiation of transition and finally a marked deceleration of growth. At high temperatures the inductance period of the transition was not observable. The transition is extremely sluggish. An apparent activation energy was calculated by the Avrami–Erofeev equation for the solid-solid transition and found to be 57.4 kJ mol−1.

特集 粉末回折法の新しい展開 １１． 湾曲型Ｘ線位置敏感検出器（ＰＳＤ）と動的構造研究

Time-resolved observations of phase transitions and solid reactions have been undertaken by angular dispersive powder diffraction at high temperature and pressure using the curved position sensitive detector (PSD) . The PSD streamer mode has a great advantage for the in situ observations of the structure changes within a few seconds because of high photon count efficiency of more than 70% and high angular resolution of 0.06° in 2θ.A Computer Aided Measurement And Control (CAMAC) System was applied to the time-resolved measurement of the diffraction intensities. An ADC having a 450MHz fast converter and histogram memory were installed in the system. The in situ observation of the pressure-induced amorphization of GeO2 using diamond anvil pressure cell and kinetic studies of dehydration of alkaline earth hydroxides at high temperature are presented in this paper.

In situ Obervation of the Pressure Induced Amorphization of GeO2.

In order to study the stability field of GeO2 under high pressure at room temperature, an in situ observation was made by using a diamond anvil pressure cell, an optical microscope and a high speed VTR. At about 6.5GPa, a transparent single-crystal of α-quartz type GeO2 quickly changed to a translucent material which was found to be X-ray amorphous. The loss of transparency induced by the transformation is attributed to the pulverization due to the large volume change (approximately 10%), which causes the increase of refractive index and introduces the imperfection into the single-crystal.

Pressure-sensitive Optical Properties of Bis(1,2-dionedioximato)-Palladium (II) Complexes.

The absorption spectra of Pd(niox)2, Pd(dmg)2 and Pd(dpg)2 have been studied at high pressures. The absorption bands based on the 4dz2-5pz transition shifted rapidly to longer wavelengths with increasing pressure. The mean rates of the red shift with pressure were ca. -1170cm-1/GPa for Pd(niox)2, ca. -1300cm-1/GPa for Pd(dmg)2 and ca. -1990cm-1/GPa for Pd(dpg)2. A new pressure-induced absorption band at around 410nm was observed for Pd(niox)2 above 10GPa. The electronic states of the palladium complexes are discussed. The colors of the complexes in the diamond-anvil pressure cell were observed visually at various pressures. The colors of the complexes turn from yellow to orange and then to successive colors in the visible spectrum with increasing pressure. These materials can be utilized as a pressure indicator over the wide pressure range.

Compressibility of RbBr at elevated pressures

Compressibility data of RbBr measured by an in situ X-ray energy-dispersive diamond-anvil pressure cell are reported. Measurements of molar volumes were made at room temperature to greater than 15 GPa. The results obtained with a pressure transmitting medium were in agreement with those of previous workers (Bridgman ( 1) and Vaidya and Kennedy ( 2)) using the piston-displacement technique at lower pressures. The results obtained without a pressure transmitting medium, but were probably hydroscopic, were systematically more compressible than those of previous workers. Measurements from this work, combined with Bridgman's ( 1) and Vaidya and Kennedy's ( 2) piston-displacement measurements to 40,000 kg/cm 2 and 45 kbar, respectively, yielded values of K° T = 13.84 ± 1.03 GPa and K°′ T = 5.24 ± 0.29.

Pressure-sensitive absorption spectra of thin films of bis(diphenylglyoximato)platinum(II), Pt(dpg)2: potential application as an indicator of pressure

The optical properties of thin films of Pt(dpg)2 have been studied at high pressures. Two absorption bands of the complex in the visible region shifted sharply to longer wavelengths with increasing pressure. The rates of the red shift with pressure were ca.–1900 cm–1 GPa–1 for the metal-to-ligand charge-transfer(M–L) band and –3000 cm–1 GPa–1 for the 5d-6p band. These values are the largest in the known one-dimensional d8 metal complexes. The colours of the thin films in the diamond-anvil pressure cell were observed visullay at various pressures. The colours of Pt(dpg)2 turned from red–brown at atmospheric pressure to brown at 0.27 GPa, green at 0.69 GPa, to yellow–green at 1.24 GPa and yellow at 1.92 GPa. This material can be utilized as an indicator of pressure over a GPa range 0–2.

Crystallite size effect on the pressure-induced phase transformation of ZrO2

An effect of crystalline size on the orthorhombic to monoclinic phase transformation of ZrO2 has been elucidated. An in situ observation of the transformation of ZrO2 samples having several crystallite sizes was undertaken under high pressure by using a diamond anvil pressure cell with the X-ray energy dispersive diffraction technique. The proportion of the transformed phase to the original phase was evaluated for each sample in the pressure range up to 10 GPa. The threshold pressure of the phase transformation was shifted toward the higher pressure side as the crystallite size decreased.

Angular dispersive diffraction using a diamond-anvil pressure cell and synchrotron X-ray source

Abstract Wavelength dispersive diffraction studies have been performed using a diamond-anvil pressure cell and bending magnet synchrotron produced radiation. A double-crystal monochromator was used to select 15 and 17 keV photons and a 80 μm diameter collimator was used to restrict the beam entering the pressure cavity. Parallelism between the incident beam and the collimator axis was assisted by computer control of the collimator. The image of the transmitted beam was observed using a Hamamatsu x-ray Vidicon and TV monitor, for this alignment. The diffracted beam was recorded on x-ray film using a double film cassette and exposure times ranged from 6 to 8 hours. Neither the exposure time nor the line width of the diffraction lines was significantly altered by replacement of the incident beam collimator with a slit system.

Diamond anvil cell for measurements in high magnetic fields

Abstract We constructed a diamond anvil cell for pressures up to 100 GPa in magnetic fields up to 12 T. The cell can be operated at any temperature between 10 and 350 K. Loading by condensation of gases is possible.

Raman modes of metastable phases of Si and Ge

Abstract We have measured Raman spectra of metastable phases of Si and Ge prepared in a diamond anvil cell for pressures up to 12 GPa. For Si we observe eight Raman lines with mode Grüneisen parameters varying between -0.3 and 1.5. These lines can be assigned to the zone-center phonons of the cubic BC8-structure (Z = 8) by assuming a violation of Raman selection rules presumably due to disorder. In the case or Ge we observe two phases with different Raman spectra. The spectrum of the first phase is strikingly similar to that of BC8-Si. Below about 5 GPa this phase transforms into a second phase, which can be identified as Ge in the hexagonal diamond structure.

Comparative compressibility of Cu, Ag and Au

X-Ray diffraction studies of the mixtures of Cu + Ag and Cu + Au were carried out at room temperature and under hydrostatic pressures over 100 kbar in a diamond-anvil pressure cell using both conventional and synchrotron X-ray sources. The difference in the d-spacings (Δ d) for the reflections having the same Miller index between these metals appears to be a linear function with pressure. Mathematical analysis yielded isothermal bulk moduli ( B 0) to be 1.167±0.007 Mb for Ag and 1.664±0.026 Mb for Au, assuming B 0 = 1.374 Mb for Cu. The results for both Cu and Au used and obtained in this study are in good agreement with those calculated from elastic constant measurements, but the bulk modulus for Ag agrees better with that derived from compressional studies than from elastic measurements.