scholarly journals Influence of copper on electrical conductivity of glass-ceramics based on vanadium dioxide

2019 ◽  
Vol 27 (1) ◽  
pp. 57-62
Author(s):  
A. I. Ivon ◽  
V. R. Kolbunov
Keyword(s):  
Phase Transition ◽  
Activation Energy ◽  
Electrical Conductivity ◽  
Vanadium Dioxide ◽  
Glass Ceramics ◽  
Vanadium Phosphate ◽  
Magnéli Phases ◽  
Oxidation Reduction ◽  
Phase Transition Temperatures ◽  
Straight Lines

The results of studying the electrical conductivity σ for the glass-ceramic systems VO2 ‒vanadium-phosphate glass (VPG) and VO2‒VPG‒SnO2 with the additions of Cu and Cu2O are presented. It is found that the jump of conductivity at the temperature of metal-semiconductor phase transition (MSPT) in VO2 (Tt = 341K) takes place only for glass-ceramics containing not more than 5 wt% of these additives. When their content exceeds 5 wt%, the VO2 content decreases sharply according to the data of differential thermal analysis. The reason for this is the oxidation-reduction reactions in the liquid phase between Cu and VO2 at ceramics synthesis. These reactions result in the appearance of Magneli phases in glass‒ceramics composition. The phase transitions in Magneli phases V4O7, V5O9, and V6O13 are indicated by the temperature dependence of σ, as bends of the straight lines in coordinates log10σ ~ 1/T at the phase transition temperatures Tt of these phases: 240K, 150K, and 130K. The activation energy of σ for T> Tt is lower than for T <Tt, which indicates a change in the structure of energy zones inherent to MSPT.

Notizen: Fluorine Diffusion and Phase Transition in Superionic Conductor KSn2F5 as Studied by 19F NMR, Electrical Conductivity and DSC

1983 ◽  
Vol 38 (5) ◽  
pp. 593-594 ◽  
Author(s):  
W. D. Basler ◽  
I. V. Murin ◽  
S. V. Chernov
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Activation Energy ◽  
Electrical Conductivity ◽  
Relaxation Time ◽  
Field Gradient ◽  
Magnetic Field Gradient ◽  
Pulsed Magnetic Field ◽  
19F Nmr ◽  
Sharp Transition

The diffusion of fluorine in KSn2F5 has been studied by T1 and T2 relaxation time measurements of 19F NMR (200-500 K) and pulsed magnetic Field gradient tech­niques (390-480 K). Near 423 K a sharp transition into the superionic state has been found, the fluorine diffusion increasing by a factor of 4 within a range of 3 K. Conduc­tivity measurements only show a change in the activation energy.

scholarly journals An explanation of apparent sudden change in the activation energy of membrane enzymes

1976 ◽  
Vol 157 (1) ◽  
pp. 279-281 ◽  
Author(s):  
A T Wynn-Williams
Keyword(s):  
Phase Transition ◽  
Activation Energy ◽  
Enzyme Activity ◽  
Sudden Change ◽  
Enzyme Activation ◽  
Lipid Phase ◽  
Lipid Solubility ◽  
Lipid Phase Transition ◽  
Lipid Mixture ◽  
Phase Transition Temperatures

If an enzyme-lipid mixture forms phases of pure lipid and enzyme-lipid solution, and enzyme activity depends on the composition of the enzyme-lipid solution, the temperature-dependence of lipid solubility in the enzyme-lipid solution leads to apparent sudden changes in enzyme activation energy without activity discontinuities at lipid phase transition temperatures.

Charge Transport and Relaxation in Triglycine Sulphate (TGS)

1997 ◽  
Vol 52 (8-9) ◽  
pp. 621-628 ◽  
Author(s):  
W. Osak
Keyword(s):  
Phase Transition ◽  
Activation Energy ◽  
Electrical Conductivity ◽  
Relaxation Time ◽  
Low Temperatures ◽  
Relaxation Times ◽  
Crystallographic Direction ◽  
Triglycine Sulphate ◽  
Temperature Range ◽  
Space Charge Limited Currents

Abstract Charging currents, J-V characteristics and electron conductivity have been measured in triglycine sulphate along three crystallographic directions: a, b and c. The measurements have been taken in a wide temperature range between −196°C and 80 °C. It is found that the charging currents have short relaxation times in the directions: a and c and a long relaxation time along the ferroelec-tric b axis. The J-V characteristics in the direction of the a and c axes have the shapes characteristic for linear dielectrics with space charge limited currents. The J-V characteristic for the b axis depends on the temperature: In the region of the phase transition the Fridkin-Kreher formula (J ∝ V4/3) is satisfied; for low temperatures characteristic agrees with SCLC theory for linear dielectrics with Gaussian traps energy distribution. The d.c. conductivity along the c axis is much higher than along the a and b axes. In the investigated temperature range, the electrical conductivity has an activation character. For −100 °C < T < −193 °C there is: σ ∝ (1/T) exp (− E/kT) . The activation energy depends both on the crystallographic direction and on the temperature-range. For low temperatures, T < −100 °C, the activation energies are very small (of the order of a few hundreds eV).

scholarly journals Reconfigurable Vanadium Dioxide Nanomembranes and Microtubes with Controllable Phase Transition Temperatures

Nano Letters ◽  
2018 ◽  
Vol 18 (5) ◽  
pp. 3017-3023 ◽  
Author(s):  
Ziao Tian ◽  
Borui Xu ◽  
Bo Hsu ◽  
Liliana Stan ◽  
Zheng Yang ◽  
...  
Keyword(s):  
Phase Transition ◽  
Vanadium Dioxide ◽  
Transition Temperatures ◽  
Phase Transition Temperatures

Effect of Cu doping on the electrical Properties of ZnTe by Vacuum Thermal Evaporation

2018 ◽  
Vol 31 (3) ◽  
pp. 20
Author(s):  
Sarmad M. M. Ali ◽  
Alia A.A. Shehab ◽  
Samir A. Maki
Keyword(s):  
Activation Energy ◽  
Electrical Conductivity ◽  
Hall Effect ◽  
Carrier Concentration ◽  
Hall Mobility ◽  
Cu Doping ◽  
Before And After ◽  
Hall Effect Measurements ◽  
Evaporation Technique ◽  
P Type

In this study, the ZnTe thin films were deposited on a glass substrate at a thickness of 400nm using vacuum evaporation technique (2×10-5mbar) at RT. Electrical conductivity and Hall effect measurements have been investigated as a function of variation of the doping ratios (3,5,7%) of the Cu element on the thin ZnTe films. The temperature range of (25-200°C) is to record the electrical conductivity values. The results of the films have two types of transport mechanisms of free carriers with two values of activation energy (Ea1, Ea2), expect 3% Cu. The activation energy (Ea1) increased from 29meV to 157meV before and after doping (Cu at 5%) respectively. The results of Hall effect measurements of ZnTe , ZnTe:Cu films show that all films were (p-type), the carrier concentration (1.1×1020 m-3) , Hall mobility (0.464m2/V.s) for pure ZnTe film, increases the carrier concentration (6.3×1021m-3) Hall mobility (2m2/V.s) for doping (Cu at 3%) film, but  decreases by increasing Cu concentration.

Optical Switching of Coherent VO2 Precipitates Embedded in Sapphire

1995 ◽  
Vol 396 ◽  
Author(s):  
L. A. Gea ◽  
L. A. Boatner ◽  
J. D. Budai ◽  
R. A. Zuhr
Keyword(s):  
Phase Transition ◽  
Vanadium Dioxide ◽  
Thermal Processing ◽  
Optical Switching ◽  
Optical Transmission ◽  
Structural Phase ◽  
Switching Behavior ◽  
New Type ◽  
Single Crystal Sapphire ◽  
Smart Surface

AbstractIn this work, we report the formation of a new type of active or “smart” surface that is produced by ion implantation and thermal processing. By co-implanting vanadium and oxygen into a single-crystal sapphire substrate and annealing the system under appropriate conditions, it was possible to form buried precipitates of vanadium dioxide that were crystallographically oriented with respect to the host AI2O3 lattice. The implanted VO2 precipitate system undergoes a structural phase transition that is accompanied by large variations in the optical transmission which are comparable to those observed for thin films of VO2 deposited on sapphire. Co-implantation with oxygen was found to be necessary to ensure good optical switching behavior.

scholarly journals Pressure-Induced Structural Phase Transition and Metallization in Ga2Se3 up to 40.2 GPa under Non-Hydrostatic and Hydrostatic Environments

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 746
Author(s):  
Meiling Hong ◽  
Lidong Dai ◽  
Haiying Hu ◽  
Xinyu Zhang
Keyword(s):  
Phase Transition ◽  
Electrical Conductivity ◽  
High Pressure ◽  
Phase Transformation ◽  
Transport Properties ◽  
Electrical Transport ◽  
Structural Phase ◽  
Structure Evolution ◽  
Systematic Research ◽  
Electrical Transport Properties

A series of investigations on the structural, vibrational, and electrical transport characterizations for Ga2Se3 were conducted up to 40.2 GPa under different hydrostatic environments by virtue of Raman scattering, electrical conductivity, high-resolution transmission electron microscopy, and atomic force microscopy. Upon compression, Ga2Se3 underwent a phase transformation from the zinc-blende to NaCl-type structure at 10.6 GPa under non-hydrostatic conditions, which was manifested by the disappearance of an A mode and the noticeable discontinuities in the pressure-dependent Raman full width at half maximum (FWHMs) and electrical conductivity. Further increasing the pressure to 18.8 GPa, the semiconductor-to-metal phase transition occurred in Ga2Se3, which was evidenced by the high-pressure variable-temperature electrical conductivity measurements. However, the higher structural transition pressure point of 13.2 GPa was detected for Ga2Se3 under hydrostatic conditions, which was possibly related to the protective influence of the pressure medium. Upon decompression, the phase transformation and metallization were found to be reversible but existed in the large pressure hysteresis effect under different hydrostatic environments. Systematic research on the high-pressure structural and electrical transport properties for Ga2Se3 would be helpful to further explore the crystal structure evolution and electrical transport properties for other A2B3-type compounds.

scholarly journals Thermal, ferroelastic, and structural properties near phase transitions of organic–inorganic perovskite type [NH3(CH2)3NH3]CdBr4 crystals

RSC Advances ◽  
2021 ◽  
Vol 11 (29) ◽  
pp. 17622-17629
Author(s):  
Ae Ran Lim
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Thermal Behavior ◽  
Structural Properties ◽  
Structural Dynamics ◽  
Transition Temperatures ◽  
Inorganic Perovskite ◽  
Phase Transition Temperatures ◽  
Perovskite Type

We studied the thermal behavior and structural dynamics of [NH3(CH2)3NH3]CdBr4 near phase transition temperatures.

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