Photoacoustic determination of phase transition in BaTiO3 induced by high pressure at room temperature

2003 ◽  
Vol 74 (1) ◽  
pp. 732-734 ◽  
Author(s):  
M. Villagrán-Muniz ◽  
M. Navarrete ◽  
E. V. Mejı́a-Uriarte
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Room Temperature

Single Crystal Growth of High-Pressure Phases of Ice and Salt Hydrate Far Below the Original Melting Point by Mixing Alcohol: Crystal Structure Determination of Magnesium Chloride Heptahydrate

2020 ◽  
Author(s):  
Keishiro Yamashita ◽  
Kazuki Komatsu ◽  
Hiroyuki Kagi
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Crystal Growth ◽  
Single Crystal ◽  
Room Temperature ◽  
Growth Technique ◽  
Salt Hydrate ◽  
X Ray

An crystal-growth technique for single crystal x-ray structure analysis of high-pressure forms of hydrogen-bonded crystals is proposed. We used alcohol mixture (methanol: ethanol = 4:1 in volumetric ratio), which is a widely used pressure transmitting medium, inhibiting the nucleation and growth of unwanted crystals. In this paper, two kinds of single crystals which have not been obtained using a conventional experimental technique were obtained using this technique: ice VI at 1.99 GPa and MgCl<sub>2</sub>·7H<sub>2</sub>O at 2.50 GPa at room temperature. Here we first report the crystal structure of MgCl2·7H2O. This technique simultaneously meets the requirement of hydrostaticity for high-pressure experiments and has feasibility for further in-situ measurements.

scholarly journals Crystalline forms of silver iodide II: Determination of phase transformations

2007 ◽  
Vol 72 (8-9) ◽  
pp. 857-868 ◽  
Author(s):  
Marija Vukic ◽  
Dragan Veselinovic ◽  
Vesna Markovic
Keyword(s):  
Phase Transition ◽  
Phase Transformations ◽  
Heating Rate ◽  
Silver Iodide ◽  
Room Temperature ◽  
Sample Heating ◽  
Crystalline Forms

In order to obtain appropriate forms of AgI (?- and ?-), a procedure was developed to synthesize AgI at room temperature (23?C), whereby samples of varying crystallographic purity and of varying crystallographic contents of the different forms were obtained. This paper presents the results of investigations of the influence of the manner of preparation of ?-AgI and ?-AgI samples and the sample heating rate on the phase transformations and their temperatures. During the heating of non-ground, ground and pressed synthesized AgI samples, the phase transformations and the corresponding temperatures for one ?-AgI and four ?-AgI samples with different ?-AgI contents (representing a crystallographic impurity) were identified. The following phase transformations were observed for the non-ground AgI samples: ?-AgI ? ?-AgI at 149.6?C (for the ?-AgI sample) and ?-AgI ? ?-AgI at 148.7?C or 148.2?C for the ?-AgI samples with a minimum content of ?-AgI (less than 7 %), as a crystallographic impurity. The phase transition ?-AgI ? ?-AgI was irreversible because ?-AgI was obtained whenever the samples were heated up to 260?C. Manual sample grinding, as well as pressing at p1 = 650 MPa and p2 = 900 MPa resulted in the ?-AgI ? ?-AgI phase transition in all the investigated cases. .

scholarly journals The Phase Transition and Dehydration in Epsomite under High Temperature and High Pressure

Crystals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 75 ◽  
Author(s):  
Linfei Yang ◽  
Lidong Dai ◽  
Heping Li ◽  
Haiying Hu ◽  
Meiling Hong ◽  
...  
Keyword(s):  
Phase Transition ◽  
Electrical Conductivity ◽  
High Pressure ◽  
High Temperature ◽  
Magnesium Sulfate ◽  
Room Temperature ◽  
Diamond Anvil Cell ◽  
Vibrational Modes ◽  
Diamond Anvil ◽  
T Phase

The phase stability of epsomite under a high temperature and high pressure were explored through Raman spectroscopy and electrical conductivity measurements in a diamond anvil cell up to ~623 K and ~12.8 GPa. Our results verified that the epsomite underwent a pressure-induced phase transition at ~5.1 GPa and room temperature, which was well characterized by the change in the pressure dependence of Raman vibrational modes and electrical conductivity. The dehydration process of the epsomite under high pressure was monitored by the variation in the sulfate tetrahedra and hydroxyl modes. At a representative pressure point of ~1.3 GPa, it was found the epsomite (MgSO4·7H2O) started to dehydrate at ~343 K, by forming hexahydrite (MgSO4·6H2O), and then further transformed into magnesium sulfate trihydrate (MgSO4·3H2O) and anhydrous magnesium sulfate (MgSO4) at higher temperatures of 373 and 473 K, respectively. Furthermore, the established P-T phase diagram revealed a positive relationship between the dehydration temperature and the pressure for epsomite.

Clinopyroxene-perovskite phase transition of FeGeO 3 under high pressure and room temperature

1999 ◽  
Vol 26 (3) ◽  
pp. 212-216 ◽  
Author(s):  
T. Hattori ◽  
T. Matsuda ◽  
T. Tsuchiya ◽  
T. Nagai ◽  
T. Yamanaka
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Room Temperature ◽  
Perovskite Phase

Single Crystal Growth of High-Pressure Phases of Ice and Salt Hydrate Far Below the Original Melting Point by Mixing Alcohol: Crystal Structure Determination of Magnesium Chloride Heptahydrate

2019 ◽  
Author(s):  
Keishiro Yamashita ◽  
Kazuki Komatsu ◽  
Hiroyuki Kagi
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Crystal Growth ◽  
Single Crystal ◽  
Room Temperature ◽  
Growth Technique ◽  
Salt Hydrate ◽  
X Ray

An crystal-growth technique for single crystal x-ray structure analysis of high-pressure forms of hydrogen-bonded crystals is proposed. We used alcohol mixture (methanol: ethanol = 4:1 in volumetric ratio), which is a widely used pressure transmitting medium, inhibiting the nucleation and growth of unwanted crystals. In this paper, two kinds of single crystals which have not been obtained using a conventional experimental technique were obtained using this technique: ice VI at 1.99 GPa and MgCl<sub>2</sub>·7H<sub>2</sub>O at 2.51 GPa at room temperature. Here we first report the crystal structure of MgCl2·7H2O. This technique simultaneously meets the requirement of hydrostaticity for high-pressure experiments and has feasibility for further in-situ measurements.

A phase transition in Ga2Se3 under high pressure

1994 ◽  
Vol 72 (9-10) ◽  
pp. 681-682 ◽  
Author(s):  
K. V. Savchenko ◽  
V. V. Shchennikov
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Thermoelectric Power ◽  
Electrical Resistance ◽  
Room Temperature ◽  
Vickers Microhardness ◽  
Zinc Blende ◽  
Stockbarger Method ◽  
Zinc Blende Structure ◽  
Semiconductor Type

Ga2Se3 crystals with an excess of Se were grown by the Bridgman–Stockbarger method and had a defect zinc blende structure with a0 = 5.42 Å [Formula: see text] (1 Å = 10−10 m). At room temperature the resistivity was equal to (4.5 ± 1.5) × 1011 Ω cm, the thermoelectric power was (−1.1 ± 0.1) mV K−1 and the Vickers microhardness was (357 ± 9) kg mm−2. The gamma-induced conductivity was measured in the gamma-emitting power range of 3–340 rad s−1. Pressure dependencies of electrical resistance and thermoelectric power at room temperature allowed us to determine a phase transition of the semiconductor–semiconductor type at 14.2 GPa.

Reversible phase transition between amorphous and crystalline in Zr41.2Ti13.8Cu12.5Ni10Be22.5 under high pressure at room temperature

2000 ◽  
Vol 76 (20) ◽  
pp. 2874-2876 ◽  
Author(s):  
Liling Sun ◽  
W. K. Wang ◽  
D. W. He ◽  
W. H. Wang ◽  
Q. Wu ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Room Temperature ◽  
Reversible Phase Transition ◽  
Reversible Phase
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