Ruthenium Doped Gadolinium Titanate: Effects of a Variable Valent Acceptor on Ionic and Electronic Conduction

1992 ◽  
Vol 293 ◽  
Author(s):  
M.A. Spears ◽  
H.L. Tuller
Keyword(s):  
Electrical Conductivity ◽  
Thermoelectric Power ◽  
Defect Structure ◽  
Oxygen Vacancies ◽  
Ionic Conduction ◽  
Electronic Conductivity ◽  
Electronic Conduction ◽  
Defect Band ◽  
Electron Migration

AbstractWe have investigated ruthenium doped gadolinium titanate, Gd2(RuxTi1-x)2O7-δ with 0 ≤ x ≤ 0.2, to determine the role of variable valent Ru in influencing the defect structure and transport properties of the pyrochlore host. We have developed a defect chemical model to interpret electrical conductivity, thermoelectric power, and thermogravimetry data. We have found that Ru acts as an acceptor compensated in large part by oxygen vacancies, resulting in enhanced ionic conduction at low values of x. For larger values (x ≈ 0.05), electronic conductivity predominates which we attribute to electron migration by hopping through a Ru-derived defect band.

scholarly journals The Effect of Defect Structure on Electrical Conductivity and Thermoelectric Power of La2-xSrxCuO4-δ at High Temperatures

2000 ◽  
Vol 68 (6) ◽  
pp. 507-514 ◽  
Author(s):  
Hideki KANAI ◽  
Takuya HASHIMOTO ◽  
Hiroaki TAGAWA ◽  
Junichiro MIZUSAKI
Keyword(s):  
Electrical Conductivity ◽  
Thermoelectric Power ◽  
High Temperatures ◽  
Defect Structure

scholarly journals Comparison of the electrical conductivity of bulk and film Ce1–xZrxO2–δ in oxygen-depleted atmospheres at high temperatures

2021 ◽  
Author(s):  
Iurii Kogut ◽  
Carsten Steiner ◽  
Hendrik Wulfmeier ◽  
Alexander Wollbrink ◽  
Gunter Hagen ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
High Temperatures ◽  
Ionic Conduction ◽  
Electronic Conductivity ◽  
Oxygen Storage ◽  
Coarse Grained ◽  
Reducing Conditions ◽  
Partial Pressures ◽  
Microstructural Effects ◽  
Defect Interactions

AbstractFeaturing high levels of achievable oxygen non-stoichiometry δ, Ce1−xZrxO2−δ solid solutions (CZO) are crucial for application as oxygen storage materials in, for example, automotive three-way catalytic converters (TWC). The use of CZO in form of films combined with simple manufacturing methods is beneficial in view of device miniaturization and reducing of TWC manufacturing costs. In this study, a comparative microstructural and electrochemical characterization of film and conventional bulk CZO is performed using X-ray diffractometry, scanning electron microscopy, and impedance spectroscopy. The films were composed of grains with dimensions of 100 nm or less, and the bulk samples had about 1 µm large grains. The electrical behavior of nanostructured films and coarse-grained bulk CZO (x > 0) was qualitatively similar at high temperatures and under reducing atmospheres. This is explained by dominating effect of Zr addition, which masks microstructural effects on electrical conductivity, enhances the reducibility, and favors strongly electronic conductivity of CZO at temperatures even 200 K lower than those for pure ceria. The nanostructured CeO2 films had much higher electrical conductivity with different trends in dependence on temperature and reducing atmospheres than their bulk counterparts. For the latter, the conductivity was dominantly electronic, and microstructural effects were significant at T < 700 °C. Nanostructural peculiarities of CeO2 films are assumed to induce their more pronounced ionic conduction at medium oxygen partial pressures and relatively low temperatures. The defect interactions in bulk and film CZO under reducing conditions are discussed in the framework of conventional defect models for ceria.

ELECTRONIC CONDUCTIVITY MEASUREMENTS IN SOLID ELECTROLYTES USING AN ION BLOCKING MICROELECTRODE: NOISE REJECTION BASED ON A MEDIAN FILTER

2013 ◽  
Vol 02 (02) ◽  
pp. 1350009 ◽  
Author(s):  
VEYIS GUNES ◽  
JEAN-YVES BOTQUELEN ◽  
ODILE BOHNKE
Keyword(s):  
Solid Electrolytes ◽  
Ionic Conduction ◽  
Median Filter ◽  
Electronic Conductivity ◽  
Conductivity Measurement ◽  
Heating System ◽  
Electronic Conduction ◽  
Oxygen Ion ◽  
Noise Rejection

In this paper, a method of electronic conductivity measurement is presented. It combines two well known methods of electrochemistry: cyclic voltammetry and chronoamperometry. This DC technique uses the Hebb–Wagner approach to block ionic conduction (when steady state conditions are reached) and allows electronic conduction of solid electrolytes to be determined. In order to get short diffusion times, a micro contact is used as an ion blocking electrode. However, as the electronic conduction in electrolytes is and should be very low, the current is also very low, typically some tens of nanoamps. Thus, the heating system inevitably generates noise problems that are solved using a median filter. As opposed to other related work, our system allows the determination of the conductivities without any preliminary smoothing or fitting of the curves (since the noise is strongly reduced). Some results with oxygen ion conductors are also given.

Role of point defects in the thermal decomposition of ammonium perchlorate

1968 ◽  
Vol 307 (1490) ◽  
pp. 303-315 ◽  
Keyword(s):  
Electrical Conductivity ◽  
Thermal Decomposition ◽  
Single Crystals ◽  
Ammonium Perchlorate ◽  
Point Defects ◽  
Defect Structure ◽  
Electrical Conductance ◽  
Charge Carriers ◽  
Point Defect Structure

The thermal decomposition of ammonium perchlorate has usually been described in terms of chemical reactions with the point defect structure of the solid ignored. Both the isothermal and adiabatic decompositions have been reinvestigated over the temperature range 200 to 450°C. There is a good correlation between the isothermal d. c. electrical conductance of single crystals, and of conductance as a function of temperature with the extent of decomposition, indicating that charge carriers play a significant role in the thermal decomposition. The study of the electrical conductivity as a function of temperature has resulted in the assignment of a probable defect structure to ammonium perchlorate: cationic Frenkel type below 250°C and Schottky disorder at higher temperatures. This suggests an explanation for the phenomenon of only 30% decomposition below 250°C and 100% above this temperature.

Revisiting the passivation of stainless steels and other passive CRAs

2018 ◽  
Vol 106 (1) ◽  
pp. 107 ◽  
Author(s):  
Jean- Louis Crolet
Keyword(s):  
Electrical Conductivity ◽  
Metal Ions ◽  
Base Metal ◽  
Stainless Steels ◽  
Electronic Conductivity ◽  
Transport Processes ◽  
General Knowledge ◽  
Inorganic Polymers ◽  
Faraday Cage

All that was said so far about passivity and passivation was indeed based on electrochemical prejudgments, and all based on unverified postulates. However, due the authors’ fame and for lack of anything better, the great many contradictions were carefully ignored. However, when resuming from raw experimental facts and the present general knowledge, it now appears that passivation always begins by the precipitation of a metallic hydroxide gel. Therefore, all the protectiveness mechanisms already known for porous corrosion layers apply, so that this outstanding protectiveness is indeed governed by the chemistry of transport processes throughout the entrapped water. For Al type passivation, the base metal ions only have deep and complete electronic shells, which precludes any electronic conductivity. Then protectiveness can only arise from gel thickening and densification. For Fe type passivation, an incomplete shell of superficial 3d electrons allows an early metallic or semimetallic conductivity in the gel skeleton, at the onset of the very first perfectly ordered inorganic polymers (- MII-O-MIII-O-)n. Then all depends on the acquisition, maintenance or loss of a sufficient electrical conductivity in this Faraday cage. But for both types of passive layers, all the known features can be explained by the chemistry of transport processes, with neither exception nor contradiction.

ROLE OF ADDED PHOSPHOGYPSUM AND HUMIC ACIDS IN THE KINETIC RELEASE OF SALT FROM SALT AFFECTED SOIL (SALINE – SODIC)

2020 ◽  
pp. 15-27
Keyword(s):  
Electrical Conductivity ◽  
Humic Acids ◽  
Release Rate ◽  
Release Kinetics ◽  
Sodium Adsorption Ratio ◽  
Salt Affected Soil ◽  
Two Factors ◽  
Dissolved Ions ◽  
Kinetic Release

In order to study the effect of phosphogypsum and humic acids in the kinetic release of salt from salt-affected soil, a laboratory experiment was conducted in which columns made from solid polyethylene were 60.0 cm high and 7.1 cm in diameter. The columns were filled with soil so that the depth of the soil was 30 cm inside the column, the experiment included two factors, the first factor was phosphogypsum and was added at levels 0, 5, 10 and 15 tons ha-1 and the second-factor humic acids were added at levels 0, 50, 100 and 150 kg ha-1 by mixing them with the first 5 cm of column soil and one repeater per treatment. The continuous leaching method was used by using an electrolytic well water 2.72 dS m-1. Collect the leachate daily and continue the leaching process until the arrival of the electrical conductivity of the filtration of leaching up to 3-5 dS m-1. The electrical conductivity and the concentration of positive dissolved ions (Ca, Mg, Na) were estimated in leachate and the sodium adsorption ratio (SAR) was calculated. The results showed that the best equation for describing release kinetics of the salts and sodium adsorption ratio in soil over time is the diffusion equation. Increasing the level of addition of phosphogypsum and humic acids increased the constant release velocity (K) of salts and the sodium adsorption ratio. The interaction between phosphogypsum and humic acids was also affected by the constant release velocity of salts and the sodium adsorption ratio. The constant release velocity (K) of the salts and the sodium adsorption ratio at any level of addition of phosphogypsum increased with the addition of humic acids. The highest salts release rate was 216.57 in PG3HA3, while the lowest rate was 149.48 in PG0HA0. The highest release rate of sodium adsorption ratio was 206.09 in PG3HA3, while the lowest rate was 117.23 in PG0HA0.

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