TY - JOUR
T1 - Oxygen nonstoichiometry and transport properties of strontium substituted lanthanum cobaltite
AU - Søgaard, Martin
AU - Hendriksen, Peter Vang
AU - Mogensen, Mogens Bjerg
AU - Poulsen, Finn Willy
AU - Skou, E.
PY - 2006
Y1 - 2006
N2 - Oxygen nonstoichiometry, structure and transport properties of the two compositions (La-0.6 Sr-0.4)(0.99)CoO3-delta (LSC40) and La0.85Sr0.15CoO3-delta (LSC15) were measured. It was found that the oxygen nonstoichiometry as a function of the temperature and oxygen partial pressure could be described using the itinerant electron model. The electrical conductivity, sigma, of the materials is high (sigma > 500 S cm(-1)) in the measured temperature range (650 - 1000 degrees C) and oxygen partial pressure range (0.209-10(-4) atm). At 900 degrees C the electrical conductivity is 1365 and 1491 S cm(-1) in air for LSC40 and LSC15, respectively. A linear correlation between the electrical conductivity and the oxygen vacancy concentration was found for both samples. The mobility of the electron-holes was inversely proportional with the absolute temperature indicating a metallic type conductivity for LSC40. Using electrical conductivity relaxation the chemical diffusion coefficient of oxygen was determined. It was found that accurate values of the chemical diffusion coefficient could only be obtained using a sample with a porous surface coating. The porous surface coating increased the surface exchange reaction thereby unmasking the chemical diffusion coefficient. The ionic conductivity deduced from electrical conductivity relaxation was determined to be 0.45 S cm(-1) and 0.01 S cm(-1) at 1000 and 650 degrees C, respectively. The activation energy for the ionic conductivity at a constant vacancy concentration (delta = 0.125) was found to be 0.90 eV. (c) 2006 Elsevier B.V. All rights reserved.
AB - Oxygen nonstoichiometry, structure and transport properties of the two compositions (La-0.6 Sr-0.4)(0.99)CoO3-delta (LSC40) and La0.85Sr0.15CoO3-delta (LSC15) were measured. It was found that the oxygen nonstoichiometry as a function of the temperature and oxygen partial pressure could be described using the itinerant electron model. The electrical conductivity, sigma, of the materials is high (sigma > 500 S cm(-1)) in the measured temperature range (650 - 1000 degrees C) and oxygen partial pressure range (0.209-10(-4) atm). At 900 degrees C the electrical conductivity is 1365 and 1491 S cm(-1) in air for LSC40 and LSC15, respectively. A linear correlation between the electrical conductivity and the oxygen vacancy concentration was found for both samples. The mobility of the electron-holes was inversely proportional with the absolute temperature indicating a metallic type conductivity for LSC40. Using electrical conductivity relaxation the chemical diffusion coefficient of oxygen was determined. It was found that accurate values of the chemical diffusion coefficient could only be obtained using a sample with a porous surface coating. The porous surface coating increased the surface exchange reaction thereby unmasking the chemical diffusion coefficient. The ionic conductivity deduced from electrical conductivity relaxation was determined to be 0.45 S cm(-1) and 0.01 S cm(-1) at 1000 and 650 degrees C, respectively. The activation energy for the ionic conductivity at a constant vacancy concentration (delta = 0.125) was found to be 0.90 eV. (c) 2006 Elsevier B.V. All rights reserved.
KW - Brændselsceller og brint
U2 - 10.1016/j.ssi.2006.09.005
DO - 10.1016/j.ssi.2006.09.005
M3 - Journal article
VL - 177
SP - 3285
EP - 3296
JO - Solid State Ionics
JF - Solid State Ionics
SN - 0167-2738
IS - 37-38
ER -