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.

RESISTIVE ANOMALIES AT NEAR 250 K IN Hg-Ca-Cu-O AND Fe-S SYSTEMS

1999 ◽  
Vol 13 (29n31) ◽  
pp. 3755-3757
Author(s):  
S. S. YOM ◽  
JONG-KU PARK ◽  
G. H. KIM ◽  
H. S. KIM ◽  
J. Y. LEE ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Magnetic Susceptibility ◽  
Mechanical Alloying ◽  
Thermoelectric Power ◽  
Thermal Hysteresis ◽  
Unknown Origin ◽  
Synthesis Condition ◽  
Nominal Composition ◽  
Rapid Drop

High pressure synthesized samples of nominal composition of Ca 2-x Hg x CuO y with x=0.10~0.20 under reductive synthesis condition showed stable and reproducible resistivity onset transition at 225~254 K accompanied by rapid drop of thermoelectric power without accompanying magnetic susceptibility transition. Fe 1-x S ( x =0) by mechanical alloying method showed resistivity anomaly and thermal hysteresis at 150~180 K. These resistive anomalies may be phase transition of unknown origin rather than an indication of superconductivity.

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.

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

PRESSURE-INDUCED METALLIZATION AND SUPERCONDUCTIVITY IN InP AND InN

2011 ◽  
Vol 25 (04) ◽  
pp. 573-587
Author(s):  
K. IYAKUTTI ◽  
V. REJILA ◽  
M. RAJARAJESWARI ◽  
C. NIRMALA LOUIS ◽  
S. MAHALAKSHMI
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Structural Phase Transition ◽  
Electronic Band Structure ◽  
Indium Nitride ◽  
Structural Phase ◽  
Superconducting Transition ◽  
Electronic Band ◽  
Zinc Blende ◽  
Lmto Method

The electronic band structure, structural phase transition, metallization and superconducting transition of cubic zinc blende-type indium phosphide ( InP ) and indium nitride ( InN ), under pressure, are studied using TB-LMTO method. These indium compounds become metals and superconductors under high pressure but before that they undergo structural phase transition from ZnS to NaCl structure. The ground-state properties and band gap values are compared with the experimental and previous theoretical results. From our analysis, it is found that the metallization pressure increases with increase of lattice constant. The superconducting transition temperatures (Tc) of InP and InN are obtained as a function of pressure for both the ZnS and NaCl structures and these compounds are identified as pressure-induced superconductors. When pressure is increased Tc increases in both the normal ( ZnS ) and high pressure ( NaCl ) structures. The dependence of Tc on electron–phonon mass enhancement factor λ shows that InP and InN are electron–phonon mediated superconductors. The non-occurrence of metallization, phase transition and onset of superconductivity simultaneously in InP and InN are confirmed.

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
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