Grain size dependence of electrical properties of Gd-doped ceria

概要

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A Gd-doped ceria powder (GDC, Ce_<0.8>Gd_<0.2>O_<1.9>) prepared from an oxalate precursor was hot-pressed at 1173-1273 Kin Ar atmosphere and annealed in air at 1273-1473K to control the bulk density and grain size. Complex impedance of GDC of the microstructures of 0.29-5.6μm average grain size and 95-98% theoretical density were measured at 573-1073K in air in the frequency range from 100Hz to 2 MHz. The bulk conductivity (σ_i(b)) was independent of the grain size and the activation energy for the migration of oxide ions was 85-88kJ/mol. The grain boundary conductivity (σ_i(g)) was far small as compare withσ_i (b) (σ_i(g)=1/40-1/700 ofσ_i(b) at 573K). Theσ_i(g) was influenced by the average grain size and showed a minimum value at around 3μm and gradually increased with decreasing grain size. However, the total conductivity decreased for smaller grain size because of the increased thickness of grain boundary of relatively low conductivity. The information of diffusion of oxide ions from the surface into GDC inside was also reported.
2008-02-01