Journal article
Oxygen Non-Stoichiometry and Electrical Conductivity of La0.2Sr0.8Fe0.8B0.2O3 − δ, B = Fe, Ti, Ta
The oxygen non-stoichiometry was determined by coulometric titration for the perovskite oxides La0.2Sr0.8FeO3 − δ and La0.2Sr0.8Fe0.8B0.2O3 − δ (B = Ti4+ and Ta5+) in the temperature range 600 °C ⩽ T ⩽ 900 °C and the oxygen partial pressure range: 1⋅10-15≤po2≤0.209 atm. The non-stoichiometry (δ) is observed to decrease with B-site substitution of Fe.
The data can be well fitted with simple defect chemistry models. At low oxygen non-stoichiometry all compositions show a deviation from a localized electrons defect model. The standard and partial molar thermodynamic quantities were obtained and a gradual transition from localized to itinerant electrons with decreasing non-stoichiometry is proposed from the δ-dependency of the configurational entropy.
The absolute value of the enthalpy of oxidation decreases upon B-site substitution of Fe proposing a decreased thermodynamic stability for the substituted materials. The electrical conductivity was measured at T = 900 °C in the oxygen partial pressure range: 1⋅10-17≤po2≤0.209 atm. The electrical conductivity and charge carrier mobility decrease upon 20% substitution of Fe roughly by a factor of 2, but do not show a significant dependence on the nature of the B-site dopant.
Language: | English |
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Publisher: | The Electrochemical Society |
Year: | 2014 |
Pages: | 20F176-F184 |
ISSN: | 19457111 and 00134651 |
Types: | Journal article |
DOI: | 10.1149/2.001403jes |
ORCIDs: | Hendriksen, Peter Vang |