Method of low-temperature optical measurements with diamond anvil cells

Abstract

Constructions of a cryogenic diamond anvil system with mechanical clamping press and helium pressure medium for microscopic optical studies are described. Low temperature nonmagnetic cells ø40 and ø20 mm have been developed. GaP samples doped with S, Te and isoelectronic impurities N, NN have been investigated up to 20 GPa at 1.5-300K.     

In situ mapping of high-pressure fluids using hydrothermal diamond anvil cells

We present new results combining high pressures and temperatures attainable in a diamond anvil cell with in situ synchrotron radiation induced micro-X-ray fluorescence measurements. Hydrothermal diamond anvil cells experiments have been performed by measuring the partitioning of Pb between aqueous fluids (pure water or NaCl-enriched water) and hydrous silicate melts of haplogranite composition using synchrotron X-ray fluorescence. The in situ measurements were performed in the range 0.3–1.2 GPa and 730–850 ^°C both in the aqueous fluid and in the silicate melts being in equilibrium. Pb is strongly partitioned into high-pressure–temperature hydrous melts when Cl is present in either the hydrous melt or the aqueous fluid. Moreover, our comparisons of in situ results with post-mortem results show that significant changes take place during rapid quenching especially when samples are small (few hundred of microns in diameter). Water exsolution is induced by the quench in the silicate melt showing the high mobility of Pb which immediately partitions into the water vapor phase during the quench. The current in situ approach offers thus a pertinent complementary method to the classical experimental petrology investigations.     

Intelligent anvils applied to experimental investigations: state-of-the-art

Since a long time, efforts have been made to improve the accuracy of pressure and temperature measurements in diamond anvil cell experiments performed in experimental petrology and high-pressure physics. Here, we report on the state-of-the-art of the research carried out during past few years with the diamond anvils carrying implanted electronic structures (‘intelligent’ anvils, iAnvils). The electronic structures are inserted a few microns below the diamond surface into the diamond lattice by high-energy implantation of boron. These structures can be used as pressure- and temperature-sensitive devices. Another useful application is the fabrication of micro-heaters integrated in the anvils. Pressure- and temperature-induced responses of the sensors (change of resistance) are quantified by low-current measurement equipment. Calibrations against pressure–temperature parameters are performed using well-known phase transitions or by using equation of state of pure substances. Results of in situ measurements performed on iAnvils under pressure and temperature are presented, together with calibration curves for pressure and temperature. Future experiments on in situ measurements of the conductivity dependence of the sensor structures are discussed.     

Optically monitored high-pressure gas loading apparatus for diamond anvil cells

We describe a high-pressure system built to load rare gases (He, Ar, Ne) in various types of diamond anvil cells, at room temperature. These gases are used as pressure transmitting media to obtain the best hydrostatic compression conditions in high-pressure experiments. Optical windows allow control of the loading process. The loading success rate is close to 100% and the initial pressures in the diamond anvil cell are in between 0.2 and 1?GPa. This system can easily be adapted for loading of various gaseous samples, including gas mixtures, which generally cannot be loaded by cryogenic methods.     

Finite-element modeling of stresses and strains in a diamond anvil cell device: case of a diamond-coated rhenium gasket

The stresses and strains in a diamond anvil cell device were investigated using a finite-element code NIKE2D for the case of an ultra-hard composite gasket material. The pressure distribution in a diamond-coated rhenium gasket was measured by the energy dispersive diffraction technique to 213 GPa and compared with the finite-element modeling results. We examine various models for the mechanical properties of diamond-coated rhenium gasket as well as for diamond failure for shear stresses exceeding 100 GPa. The elastic and plastic properties of gasket were varied such that a good agreement between the experimentally measured pressure distribution and the computational pressure profiles were obtained. As a result, we obtained the effective Young’s modulus, Poisson’s ratio, yield stress for indented gasket, linear hardening modulus, and hardening parameter value for this layered ultra-hard composite gasket material. Future diamond design strategies for attainment of extreme high pressures using ultra-hard gasket materials are also discussed.     

X-ray absorption spectroscopy under high pressures in diamond anvil cells

Abstract

Although potentially extremely important for understanding the high-pressure microscopic behaviour of materials, over the years the area of high-pressure EXAFS in particular using diamond anvil cells has proved to be technically difficult. This has significantly hampered its development. The interference of X-ray dimaction from the diamonds in the diamond anvil cell with the absorption signal has proved to be a challenging problem to tackle, restricting the use of high-pressure EXAFS to energies below about 11 key Below 11 keV however the technique is also limited due to absorption of incident X-rays by the diamonds making it virtually impossible to conduct X-ray absorption experiments below about 9keV In this paper we describe in detail the methodology for scanriirig high-pressure EXAFS in diamond anvil cells and examine the origins of the associated problems and ways of dealing with them. We also demonstrate that it is possible to extend the useful range of studied absorption edges from 7keV up to at least 30keV This brings about new opportunities for high pressure EXAFS using diamond anvil cells.     

High-pressure and high-temperature generation using diamond/sic composite anvils prepared with hot isostatic pressing

Using a hot isostatic pressing (HIP) technique, we synthesized diamond/SiC composites from diamond and Si powders. At an HIP condition of 1450 °C and 100 MPa, a pressure much lower than that of the diamond stability field, diamond powders react with molten Si to form well-sintered diamond/SiC composites. Cubes of the composites with 15 mm edge length were thereby fabricated, and an application to the second stage anvils in a Kawai-type high-pressure apparatus was attempted. A hybrid anvils system using four cubes of the composites and four of the conventional WC was introduced and heating experiments up to 1600 °C became possible. Because the diamond/SiC composites are transparent to X-rays, the present system is applicable not only to diffraction studies but also to radiographic studies that need a larger window for an X-ray image.     

金刚石压腔蛇纹石原位拉曼光谱研究

在金刚石压腔中,运用激光拉曼光谱技术对高压下蛇纹石矿物结构及其稳定性进行了原位观测与研究。实验获得蛇纹石在常温下从0.1～5 140MPa的拉曼光谱数据。研究发现,蛇纹石低频拉曼谱峰388,471,692和705cm-1随压力增加有规律地向高频偏移;层内羟基3 664cm-1峰和层间羟基3 696cm-1峰与压力呈明显的正相关性。层内羟基3 664cm-1峰随压力变化的斜率为3.3cm-1.GPa-1,层间羟基3 696cm-1峰在2.0GPa时斜率由8.3cm-1.GPa-1变为1.1cm-1.GPa cm-1。在实验温压条件下,蛇纹石未发生脱水作用。     

Study of partial melting at high-pressure using in situ X-ray diffraction

The high-pressure melting behavior of different iron alloys was investigated using the classical synchrotron-based in situ X-ray diffraction techniques. As they offer specific advantages and disadvantages, both energy-dispersive (EDX) and angle-dispersive (ADX) X-ray diffraction methods were performed at the BL04B1 beamline of SPring8 (Japan) and at the ID27-30 beamline of the ESRF (France), respectively. High-pressure vessels and pressure ranges investigated include the Paris–Edinburgh press from 2 to 17 GPa, the SPEED-1500 multi-anvil press from 10 to 27 GPa, and the laser-heated diamond anvil cell from 15 to 60 GPa. The onset of melting (at the solidus or eutectic temperature) can be easily detected using EDX because the grains start to rotate relative to the X-ray beam, which provokes rapid and drastic changes with time of the peak growth rate. Then, the degree of melting can be determined, using both EDX and ADX, from the intensity of diffuse X-ray scattering characteristic of the liquid phase. This diffuse contribution can be easily differentiated from the Compton diffusion of the pressure medium because they have different shapes in the diffraction patterns. Information about the composition and/or about the structure of the liquid phase can then be extracted from the shape of the diffuse X-ray scattering.     

Three-dimensional X-ray diffraction in the diamond anvil cell: application to stishovite

Three-dimensional X-ray diffraction can be used for characterizing the orientation, position, and strain tensor of single grains in a polycrystalline aggregate. Here, we show how the method is well suited for diamond anvil cell data with heterogeneous grain sizes, with an application to two samples of stishovite at 15 and 26 GPa. For each grain, we obtain a well-defined orientation matrix and cell parameters. Center of mass position can also be adjusted to the experimental data, with errors in the present experiment. Finally, strain tensors are adjusted for the individual grains. The stress distribution obtained is in agreement with expectations from the diamond anvil cell geometry and previous measurements of stishovite strength. Advantages and potential for improvement of the method are then discussed.     

Effect of deformation of diamond anvil and sample in diamond anvil cell on the thermal conductivity measurement

Studies show that the sample thickness is an important parameter in investigating the thermal transport properties of materials under high-temperature and high-pressure (HTHP) in the diamond anvil cell (DAC) device. However, it is an enormous challenge to measure the sample thickness accurately in the DAC under severe working conditions. In conventional methods, the influence of diamond anvil deformation on the measuring accuracy is ignored. For a high-temperature anvil, the mechanical state of the diamond anvil becomes complex and is different from that under the static condition. At high temperature, the deformation of anvil and sample would be aggravated. In the present study, the finite volume method is applied to simulate the heat transfer mechanism of stable heating DAC through coupling three radiative-conductive heat transfer mechanisms in a high-pressure environment. When the temperature field of the main components is known in DAC, the thermal stress field can be analyzed numerically by the finite element method. The obtained results show that the deformation of anvil will lead to the obvious radial gradient distribution of the sample thickness. If the top and bottom surfaces of the sample are approximated to be flat, it will be fatal to the study of the heat transport properties of the material. Therefore, we study the temperature distribution and thermal conductivity of the sample in the DAC by thermal-solid coupling method under high pressure and stable heating condition.     

In situ study of calcite-III dimorphism using dynamic diamond anvil cell

The phase transitions among the high-pressure polymorphic forms of CaCO₃ (cc-I, cc-II, cc-III, and cc-IIIb) are investigated by dynamic diamond anvil cell (dDAC) and in situ Raman spectroscopy. Experiments are carried out at room temperature and high pressures up to 12.8 GPa with the pressurizing rate varying from 0.006 GPa/s to 0.056 GPa/s. In situ observation shows that with the increase of pressure, calcite transforms from cc-I to cc-II at ～ 1.5 GPa and from cc-II to cc-III at ～ 2.5 GPa, and transitions are independent of the pressurizing rate. Further, as the pressure continues to increase, the cc-IIIb begins to appear and coexists with cc-III within a pressure range that is inversely proportional to the pressurizing rate. At the pressurizing rates of 0.006, 0.012, 0.021, and 0.056 GPa/s, the coexistence pressure ranges of cc-III and cc-IIIb are 2.8 GPa-9.8 GPa, 3.1 GPa-6.9 GPa, 2.7 GPa-6.0 GPa, and 2.8 GPa-4.5 GPa, respectively. The dependence of the coexistence on the pressurizing rate may result from the influence of pressurizing rate on the activation process of transition by reducing the energy barrier. The higher the pressurizing rate, the lower the energy barrier is, and the easier it is to pull the system out of the coexistence state. The results of this in situ study provide new insights into the understanding of the phase transition of calcite.     

Investigating the thermal conductivity of materials by analyzing the temperature distribution in diamond anvils cell under high pressure

Investigating the thermal transport properties of materials is of great importance in the field of earth science and for the development of materials under extremely high temperatures and pressures. However, it is an enormous challenge to characterize the thermal and physical properties of materials using the diamond anvil cell (DAC) platform. In the present study, a steady-state method is used with a DAC and a combination of thermocouple temperature measurement and numerical analysis is performed to calculate the thermal conductivity of the material. To this end, temperature distributions in the DAC under high pressure are analyzed. We propose a three-dimensional radiative-conductive coupled heat transfer model to simulate the temperature field in the main components of the DAC and calculate in situ thermal conductivity under high-temperature and high-pressure conditions. The proposed model is based on the finite volume method. The obtained results show that heat radiation has a great impact on the temperature field of the DAC, so that ignoring the radiation effect leads to large errors in calculating the heat transport properties of materials. Furthermore, the feasibility of studying the thermal conductivity of different materials is discussed through a numerical model combined with locally measured temperature in the DAC. This article is expected to become a reference for accurate measurement of in situ thermal conductivity in DACs at high-temperature and high-pressure conditions.     

Laser heating in diamond anvil cells: developments in pulsed and continuous techniques

Developments in continuous and pulsed laser‐heating techniques, and finite‐element calculations for diamond anvil cell experiments are reported. The methods involve the use of time‐resolved (5 ns gated) incandescent light temperature measurements to determine the time dependence of heat fluxes, while near‐IR incandescent light temperature measurements allow temperature measurements to as low as 500 K. Further optimization of timing in pulsed laser heating together with sample engineering will provide additional improvements in data collection in very high P–T experiments.     

Measurement of the temperature distribution on the surface of the laser heated specimen in a diamond anvil cell system by the tandem imaging acousto-optical filter

We demonstrate that combining the laser heating (LH) system in a diamond anvil cell (DAC) with a tandem acousto-optical tunable filter (TAOTF) allows measurement of the temperature distribution (TD) under infrared (IR, 1064?nm) LH of a specimen under high pressure in a DAC. The main component of the system is a TAOTF synchronized with a video camera. The system allows TD mapping within a temperature range of approximately 1000–2000?K on the surface of a laser-heated object (Fe plates) at high pressure in a DAC with a spatial resolution 2?µm by fitting the actual signal to Planck’s equation at each point.     

High pressure X-ray diffraction study of potassium azide

Crystal structure and compressibility of potassium azide was investigated by in-situ synchrotron powder X-ray diffraction in a diamond anvil cell at room temperature up to 37.7 GPa. In the body-centered tetragonal (bct) phase, an anisotropic compressibility was observed with greater compressibility in the direction perpendicular to the plane containing N₃⁻ ions than directions within that plane. The bulk modulus of the bct phase was determined to be 18.6(7) GPa. A pressure-induced phase transition may occur at 15.5 GPa.     

金刚石对顶砧中触点位置误差对样品电阻率测量精度的影响

利用有限元分析方法,研究了金刚石对顶砧中电极与样品接触点位置变化对范德堡法测量样品电阻率精度的影响.结果表明:当电极中心与样品边缘的间距b≤d/9(d为样品直径)时能得到精确的电阻率测量结果;当电极位置远离样品边缘而逐渐接近样品中心时,其位置变化对电阻率测量精度的影响迅速增大;相同的电极位置变化对具有较大电阻率的半导体样品电阻率测量精度的影响更明显. 关键词： 电阻率 有限元方法 金刚石对顶砧     

High-energy X-ray diffraction of a hydrous silicate liquid under conditions of high pressure and temperature in a modified hydrothermal diamond anvil cell

In situ high-energy X-ray diffraction measurements were made for the first time on a water-saturated silicate melt at high pressure and temperature. A modified hydrothermal diamond anvil cell (HDAC), designed to minimize the path length of the X-ray beam within a diamond anvil and to increase the solid angle of the diffracted beam, was used to reduce high background contributions and extend X-ray diffraction data collection in Q space. Quantitative differential pair distribution function (PDF) analysis of X-ray diffraction data show that the first measurable (Si–O) peak is 0.095 Å greater in length in the hydrous melt than in the starting glass. Contributions from the H₂O O–O correlations, as well as from the second nearest neighbor O–O correlations within the silicate melt, are evident within the second peak of the differential PDF. The procedure described opens new opportunities to directly investigate volatile-rich melts at high pressure and temperature.     

Synthesis of Ge-Sn at high pressure and high temperature in a laser-heated diamond anvil cell

Ge–Sn compound is predicted to be a direct band gap semiconductor with a tunable band gap. However, the bulk synthesis of this material by conventional methods at ambient pressure is unsuccessful due to the poor solubility of Sn in Ge. We report the successful synthesis of Ge–Sn in a laser-heated diamond anvil cell (LHDAC) at ~7.6 GPa &; ~2000 K. In situ Raman spectroscopy of the sample showed, apart from the characteristic Raman modes of Ge TO (Г) and β-Sn TO (Г), two additional Raman modes at ~225 cm^?1 (named Ge–Sn₁) and ~133 cm^?1 (named Ge–Sn₂). When the sample was quenched, the Ge–Sn₁ mode remained stable at ~215 cm^?1, whereas the Ge–Sn₂ mode had diminished in intensity. Comparing the Ge–Sn Raman mode at ~225 cm^?1 with the one observed in thin film studies, we interpret that the observed phonon mode may be formed due to Sn-rich Ge–Sn system. The additional Raman mode seen at ~133 cm^?1 suggested the formation of low symmetry phase under high P–T conditions. The results are compared with Ge–Si binary system.