Electrical Conductivity of Submicrometer Gadolinia‐Doped Ceria Sintered at 1000°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 ∼5 nm size for nanopowders calcined at 300°C for 4 h. A high densification range from ∼96% to 99% of the theoretical was achieved for the nonconventionally low‐temperature sintered pellets at 1000°C from weakly bonded particles of CGO nanopowders calcined at 300°C for 4 h without any sintering aid. The dense CGO pellets sintered at 1000°C for 4 h with an average grain size of ∼150–300 nm exhibited a promising high electrical conductivity of 2.03 × 10−2 S/cm (DEA process) and 2.17 × 10−2 S/cm (NP process), measured at 650°C, and low activation energy Ea. 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°C with a larger grain size.

Study on Electrical conductivity and Activation Energy of doped Ceria nanostructures

“…The temperature-dependent ionic conductivity of the samples obeys Arrhenius equation [18]. The Arrhenius plot is shown in Figure 7.…”

Low temperature fabrication of dense gadolinia-doped ceria electrolyte with enhanced electrical conductivity

“…8, the relative densities of the samples increase rapidly from 800 o C to 900 o C, whereas further increase of sintering temperature scarcely promotes density change. Therefore, the powder synthesized by this procedure can be totally densified at 900 o C with a relative density ~ 99.9% (average grain size, ~ 100 nm), better than the results reported before [8,14,18,20,24]. Compared with (NH 4 ) 2 CO 3 , we prepared GDC20 powders by a similar method, using NH 4 OH as precipitant, and the powder could be densified at 900 o C with a relative density only 98.8% [22].…”

“…Among typical wet-chemical synthesis methods, coprecipitation is the most overwhelming route due to its simplicity, short reaction time, and feasibility for scaling up. The powders prepared by coprecipitation always show good homogeneity with high specific surface areas, which endues them with huge surface free energy and correspondingly remarkable sintering activity [18,19]. Based on the advantages of this route, powders with superior quality could be obtained by further optimizing synthesis process, especially the vital part.…”

Effects of rapid process on the conductivity of multiple elements doped ceria-based electrolyte

“…In general, nanoparticles show a higher catalytic activity, better sinterability, better conductivity and other unusual properties contrary to that of bulk materials [18]. Lately, many chemical methods have been developed to synthesize ceria-based electrolyte nanoparticles, including precipitation [19], aerosol flame deposition [20,21], glycine-nitrate combustion [22], citric acid-based sol-gel process [23], laser evaporation [24], freeze-drying [25] and hydrothermal preparation [26] among others. The sintering temperature is substantially lowered by chemically synthesized powders and by the addition of sintering aids [15].…”