Oxygen ionic and electronic transport in Gd2-xCaxTi2O7-delta pyrochlores
authors Kharton, VV; Tsipis, EV; Yaremchenko, AA; Vyshatko, NP; Shaula, AL; Naumovich, EN; Frade, JR
nationality International
journal JOURNAL OF SOLID STATE ELECTROCHEMISTRY
author keywords fuel cell; gadolinium titanate; ionic conductivity; pyrochlore; transference number
keywords FORMER SOVIET-UNION; OXIDE FUEL-CELLS; CONDUCTIVITY; ELECTROLYTES; GD2TI2O7; ELECTROCHEMISTRY; TEMPERATURE; CONDUCTORS; MIGRATION; MEMBRANES
abstract Oxygen ion transference numbers for Gd2-x CaxTi2O7-delta (x=0.10-0.14) pyrochlore ceramics were determined at 973-1223 K by the modified e.m.f. and faradaic efficiency techniques, taking into account electrode polarization, and from the results on oxygen permeation. The ion transference numbers vary in the range 0.95-0.98 in air, increasing when the temperature or oxygen partial pressure decreases. The activation energies for the ionic and p-type electronic transport in air are 74-77 and 87-91 kJ/mol, respectively. The p-type conductivity and oxygen permeability of Gd2Ti2O7-based pyrochlores can be adequately described by relationships common for other solid electrolytes. At temperatures below 1273 K under a gradient of 10%H-2 + 90%N-2/air, average ion transference numbers for doped gadolinium titanate are not less than 0.97. Thermal expansion coefficients for Gd2-xCaxTi2O7-delta ceramics, calculated from dilatometric data in air, are in the range (10.4-10.6)x10(-6) K-1 at 400-1300 K.
publisher SPRINGER-VERLAG
issn 1432-8488
year published 2003
volume 7
issue 8
beginning page 468
ending page 476
digital object identifier (doi) 10.1007/s10008-002-0348-6
web of science category Electrochemistry
subject category Electrochemistry
unique article identifier WOS:000185202000004
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