Electrical Conductivity of Submicrometer Gadolinia-Doped Ceria Sintered at 1000 degrees C Using Precipitation-Synthesized Nanocrystalline Powders

Abstract

A simple synthetic strategy has been implemented to obtain low-temperature sintered fine grain size gadolinia-doped ceria, Ce0.9Gd0.1O1.95, (CGO) electrolyte pellets with a high density, using weakly agglomerated particles of calcined nanopowders synthesized by a homogeneous precipitation process. The precipitants used were diethylamine (DEA process) and ammonium hydroxide in neutral precipitation (NP process). X-ray diffraction patterns revealed the single-phase crystalline CGO of a fluorite-type structure. The crystalline powder was directly synthesized from solution by the DEA process at room temperature, whereas the NP process powder was crystallized upon hydrothermal treatment at an elevated temperature. Transmission electron microscopy images showed homogeneously dispersed spherical-shaped particles of similar to 5 nm size for nanopowders calcined at 300 degrees C for 4 h. A high densification range from similar to 96% to 99% of the theoretical was achieved for the nonconventionally loll-temperature sintered pellets at 1000 degrees C from weakly, bonded particles of CGO nanopowders calcined at 300 degrees C for 4 h without any sintering aid. The dense CGO pellets sintered at 1000 degrees C for 4 h with an average grain size of similar to 150-300 nm exhibited a promising high electrical conductivity of 2.03 x 10(-2) S/cm (DEA process) and 2.17 x 10(-2) S/cm (NP process), measured at 650 degrees C, and low activation energy E-a. The electrical conductivities of fine grain size low-temperature sintered CGO pellets are comparable with the literature reports of sintered pellets using sintering aids, and high-temperature sintered CGO pellets above 1300 degrees C with a larger grain size.