A new differential thermal analysis setup for measuring high pressure phase transitions (original) (raw)
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An Automated High Pressure Differential Thermal Analysis System for Phase Transformation Studies
—A piston cylinder based high pressure differential thermal analyzer system is developed to investigate phase transformations, melting, glass transitions, crystallization behavior of inorganic materials, glassy systems etc., at ambient to 4 GPa and at room temperature to 1073 K. The pressure is calibrated by the phase transition of bismuth and ytterbium and temperature is calibrated by using thermocouple data chart. The system developed is calibrated using benzoic acid, ammonium nitrate and it has a pressure and temperature control of ± 8.9 x 10-4 GPa , ± 2 K respectively. The phase transition of As x Te 100-x chalcogenides, ferrous oxide and strontium boride are studied using the indigenously developed system.
Crystals
The accurate determination of melting curves for transition metals is an intense topic within high pressure research, both because of the technical challenges included as well as the controversial data obtained from various experiments. This review presents the main static techniques that are used for melting studies, with a strong focus on the diamond anvil cell; it also explores the state of the art of melting detection methods and analyzes the major reasons for discrepancies in the determination of the melting curves of transition metals. The physics of the melting transition is also discussed.
High-pressure and high-temperature study of phase transitions in solid germanium
physica status solidi (b), 2003
A detailed investigation of the pressure and temperature dependence of the structure of stable and metastable solid Ge phases in the 0-15 GPa and 295-500 K ranges is presented. Structural results including the equation of state, characteristic of coexistence regions of diamond and b-tin structures, and appearance of metastable phases are discussed and compared with the results presently available in the literature. The isothermal bulk modulus and its derivative are evaluated using temperature-dependent equations of state for Ge I (cubic) and Ge II (b-Sn), and for the Ge III (ST12) metastable polymorph at 400 K.
Physics of the Earth and Planetary Interiors, 2004
We conducted multi-anvil experiments at simultaneous high pressures and temperatures using multiple internal pressure standards including Au, Pt, MgO, W, Mo, Pd, and Ag. Extensive synchrotron X-ray diffraction data for Au, Pt, and MgO were collected at pressures up to 28 GPa and temperatures between 300 and 2173 K. We compare pressures calculated from different pressure scales and demonstrate large discrepancies in pressure determination using different pressure standards or different thermal equations of state for the same standard. The comparison allows us to quantitatively determine the differences in pressure using different pressure scales in the high P-T experiments. Using the MgO scale of [J. Geophys. Res. 106 515] as a reference pressure scale, new Au and Pt scales are presented that are consistent with the MgO scale. We further examined the validity of the assumption of constant q value (volume dependence of the Grüneisen parameter in the Mie-Grüneisen relation) for the calculations of thermal pressures, and show that an expression of q as a function of temperature and pressure may be necessary to best fit the simultaneous high P-T data. ratory experimental data obtained at high pressure and temperature. It also allows us to make comparisons of high-pressure results produced in different laboratories using different experimental and analytical 0031-9201/$ -see front matter
Application of calorimetry on a chip to high-pressure materials
Proceedings of the National Academy of Sciences, 2007
Silicon micromachined calorimeters (''calorimeter on a chip'') are used to measure heat capacities and phase transition enthalpies for thin film, single crystal, and powder samples (5-500 g). The technology is thus compatible with the small samples produced in multianvil and large diamond anvil cells. Techniques for handling small samples and attaching them to the calorimetric devices have been developed. Initial data illustrate application to CoO and to Fe 2SiO4 olivine and spinel, a quenched high pressure phase metastable at ambient conditions. The calorimetric entropy of the olivine -spinel transition in Fe 2 SiO 4 (؊16 ؎ 5 J/mol⅐K) is in good agreement with that calculated from phase equilibrium data (؊14 ؎ 3 J/mol⅐K). A magnetic transition in iron silicate spinel, detected previously by Mossbauer spectroscopy, is seen in the calorimetric signal.
arXiv (Cornell University), 2022
The pressure reported by diamond anvil cell (DAC) and shock waves (SW) experiments in most cases do not match and hardly represent the actual pressure experienced by the examined sample. Recently, Y. Zhang et al. proposed correction procedure of the reported SW data for elemental vanadium. This approach was strongly supported by the first principles DFT-Z method, proving that this procedure is indeed reasonable. It is suggested that this procedure should also be applied to other d-electrons the transition metals Fe, Ir and Pt. Thus, the actual pressure-temperature scales in DAC and SW experiments can be corrected by taking in to account the thermal pressure shifts. In the present contribution it is further claimed that first principles ab-initio DFT and MD simulations should serve as an anchor for correcting the pressures and temperatures reported by DAC and SW experiments. It is concluded that upon deriving the actual pressure sensed by the explored sample, the thermal pressure and the temperature shifts must be taken into account when constructing melting curves. In addition, the advantage of the Lindemann-Gilvarry vs. Simon-Glatzel fitting procedure of melting curves is claimed.
High pressure melting curve of osmium up to 35 GPa
Journal of Applied Physics
The melting curve of osmium (Os) has been determined up to 35 GPa and 5800 K using a laser heated diamond anvil cell facility. Al 2 O 3 was used as the thermal insulator and pressure transmitting medium. Melting was detected by the laser speckle method, and spectroradiometric technique was employed for determination of melting temperature. The measured melting curve has been compared with available theoretical melting curves. The Simon-Glatzel fit to the experimental data agrees reasonably well with the recently reported theoretical melting curve using Z-method. The melting slope of the measured melting curve is 58.0 K/GPa at P = 0.1 MPa. The melting line of Os is seen to cross that of W around 6 GPa, making it the most refractory metal. The density dependence of Grüneisen parameter [γ(ρ)] has also been determined analytically, using the experimentally obtained melting slope.
Study of partial melting at high-pressure using in situ X-ray diffraction
High Pressure Research, 2006
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.
Journal of Physics: Condensed Matter, 2003
The high pressure and high temperature phase diagram of Ta has been studied in a laser-heated diamond-anvil cell (DAC) using x-ray diffraction measurements up to 52 GPa and 3800 K. The melting was observed at nine different pressures, being the melting temperature in good agreement with previous laser-heated DAC experiments, but in contradiction with several theoretical calculations and previous pistoncylinder apparatus experiments. A small slope for the melting curve of Ta is estimated (dT m /dP ˜ 24 K/GPa at 1 bar) and a possible explanation for this behaviour is given. Finally, a P-V-T equation of states is obtained, being the temperature dependence of the thermal expansion coefficient and the bulk modulus estimated.