Here, average La_0.6Sr_0.4Co_xFe_1-xO_3-δ (0≤x≤1) nano-particle sizes were controllably modulated from 48 to 24 nm by desiccating La_0.6Sr_0.4Co_xFe_1-xO_3-δ (0≤x≤1) precursor nitrate solutions or infiltrating La_0.6Sr_0.4Co_xFe_1-xO_3-δ (0≤x≤1) precursor nitrate solutions into Ce_0.9Gd_0.1O_1.95 (GDC) scaffolds pre-infiltrated with a large amount of GDC nano-particles.  Scanning electron microscopy, thermo-gravimetric analysis, and x-ray diffraction experiments conducted on decomposed/decomposing precursor gels within, and outside of, porous GDC scaffolds showed that desiccation and pre-infiltrated nano-GDC resulted in reduced nitrate decomposition temperatures and reduced La_0.6Sr_0.4Co_xFe_1-xO_3-δ (0≤x≤1) average particle sizes.  GDC scaffolds infiltrated with La_0.6Sr_0.4Co_xFe_1-xO_3-δ (0≤x≤1) precursor gels, desiccated with CaCl₂, and subsequently fired at 700^oC, contained high-phase purity La_0.6Sr_0.4Co_xFe_1-xO_3-δ (0≤x≤1) nano-particles with average particle sizes ranging from 31-27 nm.  GDC scaffolds pre-infiltrated with nano-GDC infiltrated particles, infiltrated with La_0.6Sr_0.4Co_xFe_1-xO_3-δ (0≤x≤1) precursor gels and subsequently fired at 700^oC, contained high-phase purity La_0.6Sr_0.4Co_xFe_1-xO_3-δ (0≤x≤1) nano-particles with average particle sizes ranging from 29-24 nm.  In contrast to comparable, standard nano-composite cathodes (NCC’s) containing 48 nm average-sized La_0.6Sr_0.4Co_xFe_1-xO_3-δ (0≤x≤1) particles and achieving polarization resistances of 0.10 Ωcm² at 640°C, the best CaCl₂-dessicated NCC’s achieved 0.10 Ωcm² at 600°C, while the best pre-infiltrated nano-GDC NCC’s achieved 0.10 Ωcm² at 540°C.

Acknowledgements

This work was supported by National Science Foundation award number CBET-1254453.

Figure 1. Scanning electron micrographs for La_0.6Sr_0.4Co_xFe_1-xO_3-δ nano-particles produced inside a GDC scaffold at 700°C for citric acid-containing precursor gels that were standard (a-e) desiccated (f-j) and pre-infiltrated nano-GDC oxide particles (k-o). Note, LSF = La_0.6Sr_0.4FeO_3-x, LSFC = La_0.6Sr_0.4Fe_0.8Co_0.2O_3-x, LSCF55 = La_0.6Sr_0.4Fe_0.5Co_0.5O_3-x, LSCF = La_0.6Sr_0.4Co_0.8Fe_0.2O_3-x, and LSC = La_0.6Sr_0.4CoO_3-x. All scale bars are 50 nm in width.