Conductivity dependence on oxygen partial pressure and transport number measurements of La2Mo2O9

2004 ◽  
Vol 822 ◽  
Author(s):  
A. Tarancón ◽  
G. Dezanneau ◽  
A. Morata ◽  
F. Peiró ◽  
J.R. Morante ◽  
...  
Keyword(s):  
Impedance Spectroscopy ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Transport Number ◽  
Soft Chemistry ◽  
Force Method ◽  
Electromotive Force Method ◽  
Ion Transport Number ◽  
Oxide Ion ◽  
Conduction Properties

AbstractTransport number measurements and impedance spectroscopy in controlled temperature and atmosphere were used to investigate the electrical properties of La2Mo2O9 sintered samples. These samples were prepared from nanocrystalline La2Mo2O9 powders as obtained from a new soft chemistry route involving the polymerisation of acrylamide. By means of the electromotive force method measurements, the sintered compound was found mainly oxygen conductor in the range of 400 °C-800 °C with oxide-ion transport number greater than 0.99. The effect of the oxygen partial pressure on the electrical conductivity of La2Mo2O9 was investigated by impedance spectroscopy from 1 to 10−22 atm, showing a highly stable conduction properties up to 10−17 atm at 800 °C.

THE ELECTRICAL PROPERTIES OF ALUMINA AT HIGH TEMPERATURES

1966 ◽  
Vol 44 (8) ◽  
pp. 1685-1698 ◽  
Author(s):  
T. Matsumura
Keyword(s):  
Electrical Conductivity ◽  
Electrical Properties ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Single Crystal ◽  
Transport Number ◽  
Ionic Transport ◽  
Mixed Conductor ◽  
Polycrystalline Alumina ◽  
Ionic Transport Number

The ionic transport number and the d-c. electrical conductivity of single-crystal and polycrystalline alumina have been studied between 1 000 °K and 1 750 °K at an oxygen partial pressure of 0.2 atm. The ionic transport number was determined by the galvanic-cell e.m.f. measurements; the electrical conductivity was measured by the three-terminal method.It was found that alumina is a mixed conductor, being predominantly an ionic conductor at temperatures below 1 100 °K and predominantly electronic at temperatures higher than 1 600 °K. The activation energies found for the electrical conductivity of the single-crystal and polycrystalline specimens are 0.8 eV and 2.4 eV respectively in the ionic range and 3.0 eV and 3.7 eV in the electronic range.

A.C. Impedance and Transport Number Measurements of Ba6 Ta2O11

1990 ◽  
Vol 210 ◽  
Author(s):  
Takashi Goto ◽  
A.R. West
Keyword(s):  
Activation Energy ◽  
Electrical Conductivity ◽  
Solid State ◽  
Impedance Spectroscopy ◽  
Transport Number ◽  
Bulk Conductivity ◽  
Concentration Cell ◽  
Boundary Conductivity ◽  
Oxygen Ion ◽  
Ion Transport Number

AbstractBa6Ta2O11 with an oxygen—deficient perovskite—related structure, was prepared through solid state reaction of BaCO3 and Ta2O5 powders. The electrical conductivity of sintered Ba6Ta2O11 pellets was measured by a.c. impedance spectroscopy inthe temperature range between 200 and 800ºC. The conductivity at 800ºC was3.7x10-3 Ω-1 cm-1; the activation energy for bulk conduction was 0.93 eV at temperatures between 500 and 800ºC and 1.22 eV below 500ºC. The bulk conductivity was independent of atmosphere, while the grain boundary conductivity, with an activation energy of 1.08 eV, decreased as oxygen partial pressure increased. The oxygen ion transport number obtained from concentration cell measurements was 0.5 to 0.65 at temperatures from 450 to 820ºC.

Iron Manganites Synthesis by the Soft Chemistry Method

2001 ◽  
Vol 674 ◽  
Author(s):  
Herve Coradin ◽  
Sophie Guillemet-Fritsch ◽  
Fabrice Agnoli ◽  
Philippe Tailhades ◽  
Abel Rousset
Keyword(s):  
Low Temperature ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Mixed Valence ◽  
High Specific Surface Area ◽  
Soft Chemistry ◽  
Oxalate Precursor ◽  
Chemistry Method ◽  
Phase Spinel ◽  
Precursor Powders

ABSTRACTThe iron manganites FexMn(3−x)O4 synthesis by soft chemistry method have been studied. The main difficulty is to obtain single phase spinel with high Mn content (0.4< x < 1.3). Oxalate precursor powders of these materials with controlled shape and nanoscopic size have been prepared. The precursors are then heat treated with a H2/H2O/N2 gas mixture at low temperature. The resulting stoechiometric spinels are metastable phases with high specific surface area and are highly reactive toward oxygen. Therefore, these oxide can be oxidized in air at low temperature in order to produce mixed valence defect manganites FexMn(3−x)O4+δ with a good reproducibility on the oxygen content. Although, some problems persist for the higher Mn contents, as the oxygen partial pressure for the reduction must be controlled precisely in order to produce the stoechiometric spinel at low temperature. The development of a low temperature reduction system, with oxygen partial pressure controlled by oxygen electrochemical pumping, is in progress.

Electrical Conduction Properties of Liquid Vanadates. I. Vanadium Pentoxide

1972 ◽  
Vol 50 (17) ◽  
pp. 2865-2870 ◽  
Author(s):  
R. C. Kerby ◽  
J. R. Wilson
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Temperature Coefficient ◽  
Vanadium Pentoxide ◽  
Electrical Conduction ◽  
Pressure Coefficient ◽  
Positive Temperature ◽  
Temperature Range ◽  
Partial Pressures ◽  
Conduction Properties

The electrical conductivity of liquid vanadium pentoxide was measured as a function of temperature and oxygen partial pressure. A positive temperature coefficient and a negative oxygen partial pressure coefficient of conduction were found for the temperature range 670 to 1000 °C and oxygen partial pressures from 0.1 to 1.0 atm. The activation energy of conduction was 0.77 eV and the oxygen partial pressure coefficient was −0.16. At oxygen partial pressures less than 0.1 atm, for the same temperature range, a negative temperature coefficient and a negative oxygen partial pressure coefficient of conduction were found.An n-type semiconduction model was used to explain the electrical conduction properties of liquid vanadium pentoxide at oxygen partial pressures greater than 0.1 atm. At lower oxygen partial pressures, electrical conduction was considered to occur by collective-electron conduction in partially filled 3d bands, due to an overlapping of the diffuse valence and conduction bands. The overlapping could result from a decrease in the cation separation distance in the melt due to the removal of oxygen ions from the melt.

Electrical Conduction Properties of Liquid Vanadates. II. The Sodium Vanadates

1972 ◽  
Vol 50 (17) ◽  
pp. 2871-2876 ◽  
Author(s):  
R. C. Kerby ◽  
J. R. Wilson
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Electrical Conduction ◽  
Ionic Conduction ◽  
Pressure Coefficient ◽  
Sodium Oxide ◽  
Liquid Sodium ◽  
Oxide Concentration ◽  
Increasing Temperature ◽  
Conduction Properties

The liquid sodium vanadates exhibited n-type semiconduction properties at sodium oxide concentrations less than 10 mol% and ionic conduction properties at concentrations greater than 25 mol%. The transition from semiconduction to ionic conduction occurred gradually as the sodium oxide concentration increased. The activation energy of conduction decreased with increasing sodium oxide concentration and increasing temperature. Negative oxygen partial pressure coefficients of conduction were found for sodium oxide concentrations less than 25 mol%. The oxygen partial pressure coefficient decreased with increasing temperature and sodium oxide concentration. The electrical conduction mechanism was considered to change from delocalized electron or polaron movement between V4+ and V5+ centers for the semiconducting liquid sodium vanadates to the probable movement of sodium and oxygen ions as the charge-carrying species forthe ionic liquid sodium vanadates.

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