Electrical properties of dense and nanocrystalline Sm³⁺-doped Ce_1−xSm_xO_2−δ (0.05 ≤ x ≤ 0.3) electrolytes for IT-SOFCs

Abstract

Sm³⁺-doped Ce_1−xSm_xO_2−δ (0.05 ≤ x ≤ 0.3) nano-sized powders for solid electrolytes were synthesized by a solution combustion method, using aspartic acid as a combustion fuel. The calcined Ce_1−xSm_xO_2−δ powders were a ceria-based single phase with a cubic fluorite structure. The nano-sized Ce_1−xSmxO_2−δ powders provided a high density, ultra-fine grain size, and high electrical conductivity even at a low sintering temperature of 1400 °C. The grain size and relative density of the Ce_1−xSm_xO_2−δ pellets ranged from 329 nm to 496 nm and from 91.9 % to 99.2 %, respectively. The grain size and density of the Ce_1−xSm_xO_2−δ pellets decreased with an increase of Sm³⁺ content. The electrical conductivity of the Ce_1−xSmxO_2−δ increased with an increase of Sm³⁺ content up to x = 0.25 and then decreased with higher Sm³⁺ content. The maximal electrical conductivity (0.105 Scm⁻¹) was obtained with Ce_0.75Sm_0.25O_2−δ at 800 °C.