Low Frequency Dielectric Relaxation and Charge Transport in Bi12TiO20 Photorefractive Sillenite Crystals

2017 ◽  
Vol 753 ◽  
pp. 163-167
Author(s):  
Rene Alejandro Castro ◽  
Nadezhda Ivanovna Anisimova ◽  
Liliya Ansafovna Nabiullina ◽  
Evgeny Borisovich Shadrin
Keyword(s):  
Charge Transport ◽  
Dielectric Relaxation ◽  
Transport Mechanism ◽  
Low Frequency ◽  
Frequency Range ◽  
Thermally Activated ◽  
Relaxation Polarization ◽  
Polarization Mechanism ◽  
Frequency Relaxation ◽  
Thermally Activated Process

Features of processes of a dielectric relaxation and charge transport in photorefractive sillenite crystals Bi12TiO20 at low frequency range are investigated. It was found that the dispersion of dielectric permittivity ε' in crystals Bi12TiO20 is characterized by its growth with lowering frequency and rising temperature. This behaviour may be related to existence of dipole-relaxation polarization mechanism. The frequency dependence of dielectric loss tgδ reveals the existence of low frequency relaxation peaks in the studied temperature range. From the conductivity dependence on the frequency and temperature it was found that conductivity σ increases as frequency increases in the low frequency range. The observed dependence σ(ω)≈Аωs indicates that transport mechanism is due to hopping of carriers via localized electron states. The charge transport is thermally activated process in which activation energy Ea = (0.82±0.03) eV.

Dielectric Property of Laminated AlN/BN Ceramic Composites

2009 ◽  
Vol 620-622 ◽  
pp. 359-362
Author(s):  
Tao Zhang ◽  
Hai Yun Jin ◽  
Rui Zhou ◽  
Ji Feng Zhao ◽  
Zhi Hao Jin
Keyword(s):  
Dielectric Property ◽  
Dielectric Loss ◽  
Low Frequency ◽  
Ceramic Composites ◽  
Space Charge Polarization ◽  
Frequency Range ◽  
Pressing Temperature ◽  
Polarization Mechanism ◽  
The Relationship ◽  
Dielectric Loss Increase

The relationship between the processing technology and the dielectric property of the laminated AlN/h-BN ceramic composites has been studied. The results showed that the main polarization mechanism of laminated ceramic composites in low frequency range is space charge polarization at the interface of AlN layer and BN layer. Due to the affection of porosity, the permittivity increases and the dielectric loss decreases with increasing the hot pressing temperature. The permittivity increases and the dielectric loss decreases with increasing thickness ratio of different layer., Both permittivity and dielectric loss increase with increasing the content of AlN doping in BN layer.

Study of the Molecular Mobility of Polysaccharide Solid Thin Layers by Dielectric Relaxation Spectroscopy

1997 ◽  
Vol 500 ◽  
Author(s):  
K. Liedermann ◽  
L. Lapčík ◽  
S. Desmedt
Keyword(s):  
Dielectric Relaxation ◽  
Low Frequency ◽  
Thin Layers ◽  
Side Chain ◽  
Relaxation Processes ◽  
Dielectric Relaxation Spectroscopy ◽  
Frequency Range ◽  
Polar Groups ◽  
Calculated Activation Energy ◽  
Β Relaxation

ABSTRACTTemperature dependence of measured dielectric relaxation spectra (DRS) in the frequency range 20 Hz - 1 MHz of hydroxyethylcellulose (HEC) are in the temperature range 100 – 350 K. of Arrhenius character with one relaxation process at 150 – 250 K. This process reflects most probably β-relaxation of the side chain groups. Calculated activation energy of this process was 5730 kJ/mole. Four types of polysaccharides were studied at 293 K temperature: hyaluronic acid (HA), chondroitin sulfate (CHS), HEC and carboxymethylcellulose (CMC), in the low-frequency range 10−5 - 100 Hz. Measured dielectric spectra were interpreted as sum of one A.C. conductivity process and of up to two relaxation processes. The relaxation processes were described by means of the Havriliak-Negami formula and their parameters were related to the molecular structure of the polymers. The low value of a in CHS is related to its strong coupling due to the presence of two polar groups in its monomeric unit, whereas low values of α × β are interpreted as being due to the strong steric hindrances caused by long pendants present in HEC.

Low Frequency Relaxation Effect Observed in Al-Mg Alloy

2012 ◽  
Vol 184 ◽  
pp. 149-154 ◽  
Author(s):  
N. Benyahia ◽  
Michel Gerland ◽  
C. Belamri ◽  
Andre Rivière
Keyword(s):  
Low Frequency ◽  
Relaxation Effect ◽  
Solution Temperature ◽  
Transient Effects ◽  
Mechanical Spectroscopy ◽  
Slow Cooling ◽  
Thermally Activated ◽  
Measurement Experiment ◽  
Frequency Relaxation ◽  
Large Frequency

Al-12 wt% Mg alloys have been studied by isothermal mechanical spectroscopy. The samples were quenched then annealed at various temperatures. Experiments were performed in a very large frequency range (10-4Hz – 50 Hz) between room and solidus temperatures. For each temperature of measurement, experiment started after complete microstructure stabilization of the sample and therefore the transient effects due for instance to β (( and β′ precipitation were not observed. Nevertheless, a new relaxation effect was obtained in the reversion temperature range. This effect is not thermally activated. It is maximal at about 0.1 Hz and increases with the temperature of measurement. It completely disappears after annealing at solid solution temperature and successive slow cooling and therefore is linked to the β precipitates. This effect is interpreted as a phase transformation at the precipitate surface induced by the applied stress.

scholarly journals Dielectric and Conduction Processes and Behaviours in Ni0.3Zn0.7Fe2O4

2016 ◽  
Vol 846 ◽  
pp. 311-317
Author(s):  
Mohd Noor Mat ◽  
M.K. Halimah ◽  
Wan Mohd Daud Wan Yusoff ◽  
H. Mansor ◽  
H. Nizam ◽  
...  
Keyword(s):  
Activation Energy ◽  
Zinc Oxide ◽  
Iron Oxide ◽  
Dielectric Properties ◽  
Dielectric Relaxation ◽  
Relaxation Process ◽  
Peak Frequency ◽  
Frequency Range ◽  
Dielectric Relaxation Process ◽  
Frequency Relaxation

Dielectric relaxation and conductivity of Ni0.3Zn0.7Fe2O4 (NZF) were studied in the frequency range between 0.01 Hz to 3 MHz and temperature range within 313 K to 473 K. The sample was prepared by mixing Zinc Oxide, Nickel Oxide and Iron Oxide and sintered at 1573 K for 10 hours long. Dielectric properties were studied using Novo Control Dielectric Spectrometer. Dielectric relaxation and conductivity phenomena were discussed using an empirical model to key out the dielectric relaxation process. Analyze peak frequency relaxation process consist of four slopes to explain the dielectric relaxation process. The conductivity of the sample indicates an activated process and activation energy of dc conductivity is 0.44 ± 0.01 eV.

MECHANISM OF ELECTRICAL CONDUCTION THROUGH SINGLE OLIGOTHIOPHENE MOLECULES

2010 ◽  
Vol 03 (04) ◽  
pp. 245-248 ◽  
Author(s):  
SEE KEI LEE ◽  
RYO YAMADA ◽  
HIROKAZU TADA ◽  
SHOJI TANAKA
Keyword(s):  
Charge Transport ◽  
Scanning Tunneling Microscope ◽  
Transport Mechanism ◽  
Electrical Conductance ◽  
Scanning Tunneling ◽  
Break Junction ◽  
Charge Transport Mechanism ◽  
Transport Mechanisms ◽  
Thermally Activated ◽  
Molecular Length

The temperature dependence of electrical conductance of oligothiophene molecules with the length of 2.2 nm (5-mer), 5.6 nm (14-mer) and 6.7 nm (17-mer) was measured by break junction method with a scanning tunneling microscope to clarify the charge transport mechanisms. The conductance of 17-mer molecule increased exponentially with temperature whereas the conductance of 5-mer and 14-mer molecules did not change. These results indicate that the dominant charge transport mechanism changed from tunneling to thermally activated hopping at molecular length around 6.7 nm (17-mer).

scholarly journals Two distinct dielectric relaxation mechanisms in the low-frequency range in Bi5TiNbWO15 ceramics

2006 ◽  
Vol 88 (16) ◽  
pp. 162908 ◽  
Author(s):  
Z. G. Yi ◽  
Y. X. Li ◽  
Y. Wang ◽  
Q. R. Yin
Keyword(s):  
Dielectric Relaxation ◽  
Low Frequency ◽  
Frequency Range

Physical Insights on Charge Transport Mechanism and the LF Noise Behavior in Oxidized Si Structures with Ge Nanoclusters

2016 ◽  
Vol 39 ◽  
pp. 105-113
Author(s):  
Vladimir Lysenko ◽  
Yurii V. Gomeniuk ◽  
Valeriya N. Kudina ◽  
Nikolay Garbar ◽  
Sergey Kondratenko ◽  
...  
Keyword(s):  
Charge Transport ◽  
Transport Mechanism ◽  
Physical Mechanism ◽  
Low Frequency ◽  
Localized States ◽  
Frequency Noise ◽  
Strong Temperature Dependence ◽  
Charge Transport Mechanism ◽  
Dc And Ac Conductivity ◽  
Charge Hopping

To ascertain physical mechanism of charge transport in Si/SiOx structures with Ge nanoclusters the measurements of their DC and AC conductivity, and also the low-frequency measurements were performed. It was revealed that in the temperatures range 110 – 250 K the characteristics measured are governed by the hopping mechanism of charge transport. The model proposed suggests that the charge hopping becomes possible due to the band of localized states inducing in the bandgap of silicon substrate when Ge nanoclusters are introduced. The model was used to estimate some parameters of hopping transport. Also, the analysis of the low-frequency noise measured for Si/SiOx structures with Ge nanoclusters allowed to ascertain the mechanism of charge hopping resulting in strong temperature dependence of the 1/f noise measured.

Ionic Space Charge Relaxation and High Dielectric Permittivity in Polyethylene Oxide

1998 ◽  
Vol 548 ◽  
Author(s):  
A. Wagner ◽  
H. Kliem
Keyword(s):  
Relative Humidity ◽  
Dielectric Permittivity ◽  
Space Charge ◽  
Polyethylene Oxide ◽  
Transition Probability ◽  
Low Frequency ◽  
Frequency Range ◽  
Molecular Weights ◽  
Thermally Activated ◽  
High Dielectric

ABSTRACTThin films (0.3μm to 11.2 μm) of Polyethylene Oxide (PEO) with molecular weights from 6 × 103 to 4 × 105 were prepared from aqueous solutions by a spin technique as AI-PEO-AI structures, or as AI-PEO-Si structures. Dielectric measurements (capacitance and loss angle) were carried out in a frequency range 3 mHz ≤ f ≤ 1 MHz in atmospheres of different relative humidity (0% r.h. to 75% r.h.) and at different temperatures (293 K to 323 K). The nominal dielectric permittivity exhibits a remarkable dependence on the sample thickness and the relative humidity. We find a true volume polarization in the high frequency range and a thermally activated relaxation process in the low frequency range, whose time constant is shifted towards high frequencies with increasing r.h.. It is considered that due to the absorbed dipolar water molecules chemical bonds within the sample are broken and quasi-free ions are generated. These ions move through the sample to the electrode interfaces and form an ionic space charge. We assume that at the PEO-Al interface an oxide layer is formed, which is impermeable for these ions. The transit times and the drift velocities of the ions are almost independent of the electric field strength in the low-field limit. Therefore we conclude that the movement of the ions can be described by a multiwell potential model, where the transition probability between neighbored wells is thermally activated.

scholarly journals Ionische dielektrische Relaxationsprozesse in Festkörpern, I / Ionic Dielectric Relaxation Processes in Solids, I

1973 ◽  
Vol 28 (11-12) ◽  
pp. 721-730 ◽  
Author(s):  
Günter Schön
Keyword(s):  
Activation Enthalpy ◽  
Low Frequency ◽  
Life Time ◽  
Relaxation Processes ◽  
Dielectric Measurements ◽  
Frequency Range ◽  
Kcal Mole ◽  
Type Layer ◽  
Frequency Relaxation ◽  
Cation Sites

Dielectric measurements have been made on single-crystals of mica-type layer silicates (vermiculites) in the frequency range between 30 Hz and 10 MHz. The migration of K+-and NH4+-interlayer cations by free cation sites causes a low-frequency relaxation. It is interpreted by the orientation of large dipoles they form with parent negative layer charges. For both ions the activation enthalpy of diffusion across the lattice is 11.94 kcal/mole. Additional N-H · · · O hydrogen bonds are formed by the NH4+ ions at low temperatures. There results a bond enthalpy of 1.3 kcal/mole and a life-time of 1.2 · 10-5 sec (at 40°C). A discussion of the different rate process equations yields the applicability of the Bauer equation.

Sign in / Sign up

Export Citation Format

Share Document