dcProton conductivity at low-frequency in Nafion conductivity spectrum probed by time-resolved SAXS measurements and impedance spectroscopy

2015 ◽  
Vol 53 (11) ◽  
pp. 822-828 ◽  
Author(s):  
Bruno R. Matos ◽  
Elisabete I. Santiago ◽  
Jose Fernando Q. Rey ◽  
Carlos H. Scuracchio ◽  
Gerson L. Mantovani ◽  
...  
Keyword(s):  
Impedance Spectroscopy ◽  
Low Frequency ◽  
Conductivity Spectrum ◽  
Time Resolved

scholarly journals Study of Influence of Electrode Geometry on Impedance Spectroscopy

2010 ◽  
Author(s):  
Riaz Ahmed ◽  
Kenneth Reifsnider
Keyword(s):  
Impedance Spectroscopy ◽  
High Frequency ◽  
Low Frequency ◽  
Effective Area ◽  
Ac Impedance ◽  
Local Geometry ◽  
Electrode Geometry ◽  
Electrode Area ◽  
Impedance Response ◽  
Working Electrode

Electrochemical Impedance Spectroscopy (EIS) is a powerful and proven tool for analyzing AC impedance response. A conventional three electrode EIS method was used to perform the investigation in the present study. Saturated potassium chloride solution was used as the electrolyte and three different material rods were used as working electrodes. Different configurations of electrode area were exposed to the electrolyte as an active area to investigate electrode geometry effects. Counter to working electrode distance was also altered while keeping the working electrode effective area constant to explore the AC response dependence on the variation of ion travel distance. Some controlled experiments were done to validate the experimental setup and to provide a control condition for comparison with experimental results. A frequency range of 100 mHz to 1 MHz was used for all experiments. In our analysis, we have found a noteworthy influence of electrode geometry on AC impedance response. For all electrodes, impedance decreases with the increase of effective area of the electrolyte. High frequency impedance is not as dependent on geometry as low frequency response. The observed phase shift angle drops in the high frequency region with increased working electrode area, whereas at low frequency the reverse is true. Resistance and capacitive reactance both decrease with an increase of area, but resistance response is more pronounce than reactance. For lower frequencies, small changes in working area produce very distinctive EIS variations. Electrode material as well as geometry was systematically varied in the present study. From these and other studies, we hope to develop a fundamental foundation for understanding specific changes in local geometry in fuel cell (and other) electrodes as a method of designing local morphology for specific performance.

scholarly journals Theta activity paradoxically boosts gamma and ripple frequency sensitivity in prefrontal interneurons

2021 ◽  
Vol 118 (51) ◽  
pp. e2114549118
Author(s):  
Ricardo Martins Merino ◽  
Carolina Leon-Pinzon ◽  
Walter Stühmer ◽  
Martin Möck ◽  
Jochen F. Staiger ◽  
...  
Keyword(s):  
Low Frequency ◽  
Gamma Oscillations ◽  
Brain State ◽  
Gabaergic Interneurons ◽  
Time Resolved ◽  
Cortical Rhythms ◽  
Brain States ◽  
Fast Spiking ◽  
Fast Oscillations ◽  
Cross Frequency Coupling

Fast oscillations in cortical circuits critically depend on GABAergic interneurons. Which interneuron types and populations can drive different cortical rhythms, however, remains unresolved and may depend on brain state. Here, we measured the sensitivity of different GABAergic interneurons in prefrontal cortex under conditions mimicking distinct brain states. While fast-spiking neurons always exhibited a wide bandwidth of around 400 Hz, the response properties of spike-frequency adapting interneurons switched with the background input’s statistics. Slowly fluctuating background activity, as typical for sleep or quiet wakefulness, dramatically boosted the neurons’ sensitivity to gamma and ripple frequencies. We developed a time-resolved dynamic gain analysis and revealed rapid sensitivity modulations that enable neurons to periodically boost gamma oscillations and ripples during specific phases of ongoing low-frequency oscillations. This mechanism predicts these prefrontal interneurons to be exquisitely sensitive to high-frequency ripples, especially during brain states characterized by slow rhythms, and to contribute substantially to theta-gamma cross-frequency coupling.

scholarly journals Monoclinic Li2TiO3 Nano-particles via sol-gel method: Structure and impedance spectroscopy

2019 ◽  
Vol 8 (3) ◽  
pp. 209
Author(s):  
Fatima Zahra Krimech ◽  
Salaheddine Sayouri ◽  
Taj-Edine Lamcharfi ◽  
Fatima Zahra Ahjyaje
Keyword(s):  
Impedance Spectroscopy ◽  
Sol Gel ◽  
Low Frequency ◽  
Transport Processes ◽  
Nano Particles ◽  
Secondary Phases ◽  
Conventional Solid State Reaction ◽  
Gel Method ◽  
Sol Gel Method ◽  
Heat Treated

<p>Pure phase Li<sub>2</sub>TiO<sub>3 </sub>nano-particles were synthesized by the sol-gel method and the structural properties were examined with X-ray diffraction (XRD) technique. The latter showed that these materials, heat treated at relatively low temperature 900°C during 4h compared to the conventional solid-state reaction which calcination temperature is about 900–1100°C for 10 h; crystallize in the monoclinic phase without the presence of secondary phases. The microstructure of the LT ceramic (sintered at 1100°C) were determined by SEM and a good crystalline nature was observed with an average of granular size 2 μm. Moreover, the impedance spectroscopy showed at a higher temperature of 500°C the low-frequency arc due either to the grain boundary or sample-electrode charge transport processes.</p>

EFFECT OF BARIUM ON DIELECTRIC, FERROELECTRIC, IMPEDANCE AND ELECTRICAL MODULUS PROPERTIES OF Bi0.5Na0.5TiO3 CERAMICS

2011 ◽  
Vol 25 (22) ◽  
pp. 2931-2948 ◽  
Author(s):  
K. SAMBASIVA RAO ◽  
K. CH. VARADA RAJULU ◽  
B. TILAK
Keyword(s):  
Power Law ◽  
Single Phase ◽  
Low Frequency ◽  
Rhombohedral Structure ◽  
Conductivity Spectrum ◽  
X Ray ◽  
Impedance Spectroscopy Study ◽  
Conventional Sintering ◽  
Phase Compound ◽  
Jonscher’S Power Law

Perovskite structured ferroelectric ( Na 1/2 Bi 1/2)0.945 Ba 0.055 TiO 3 (BNBT-5.5) material has been synthesized by the conventional sintering technique. X-ray analysis on the material showed a single phase compound with rhombohedral structure with lattice parameters a = 3.89 Åand α = 89.893 Å. Frequency and temperature dependence of dielectric permittivity, impedance, modulus and conductivity have been performed in the frequency and temperature range 45 Hz–5 MHz and 35–595°C, respectively. The observed low frequency dielectric dispersion (LFDD) in the material could be explained by Jonschers power law and evaluated activation energies at different temperature regions. Impedance spectroscopy study showed the presence of both bulk and grain boundary effects in the materials. The ac conductivity spectrum obeyed the Jonscher's power law. Modulus analysis indicated the possibility of hopping mechanism for electrical process in the system.

Low-Frequency Dielectric Property and Impedance Spectroscopy of Bismuth-Lanthanum-Titanate Ceramics with Nb Doping

2008 ◽  
Vol 52 (2) ◽  
pp. 410-414 ◽  
Author(s):  
Jin Soo Kim ◽  
Byung Chun Choi ◽  
Jong Won Chung ◽  
Jung Hyun Jeong ◽  
Sang-Bock Cho
Keyword(s):  
Dielectric Property ◽  
Impedance Spectroscopy ◽  
Low Frequency ◽  
Lanthanum Titanate ◽  
Nb Doping ◽  
Titanate Ceramics
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