Details

Autor(en) / Beteiligte

• Bowman, William J.
• Zhu, Jiangtao
• Sharma, Renu
• Crozier, Peter A.

Titel

Electrical conductivity and grain boundary composition of Gd-doped and Gd/Pr co-doped ceria

Ist Teil von

• Solid state ionics, 2015-04, Vol.272, p.9-17

Erscheinungsjahr

2015

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• We characterize electrical conductivity, microstructure, nano-scale grain boundary structure and chemistry of ceria electrolytes with nominal compositions of Gd sub(0.2)Ce sub(0.8)O sub(2- delta ) (GDC) and Gd sub(0.11)Pr sub(0.04)Ce sub(0.85)O sub(2- delta ) (GPDC). The electrolytes are fabricated using mixed oxide nanopowders synthesized by spray drying. AC impedance spectroscopy was performed from 150 [degrees]C to 700 [degrees]C in air to determine grain-interior electrical conductivity. Grain-boundary conductivity was determined below 300 [degrees]C. The grain-interior conductivity of the GPDC was higher than that of GDC by as much as 10 times, depending on the temperature. The GPDC specific grain-boundary conductivity was measured to be approximately 100 times higher than that of GDC. Energy dispersive X-ray spectroscopy (EDX) and electron energy-loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM) confirmed the grain-to-grain compositional uniformity of both materials following heat treatments. Grain boundaries were free of glassy intergranular phases; dopant concentration and Ce oxidation state were found to vary significantly near grain boundaries. Boundary core composition was estimated from STEM EELS to be Gd sub(0.62)Ce sub(0.38)O sub(2- delta ), and Gd sub(0.29)Pr sub(0.16)Ce sub(0.55)O sub(2- delta ) in GDC and GPDC, respectively. Pr segregation to grain boundaries in the GPDC is hypothesized to enhance conductivity by both decreasing oxygen vacancy migration energy, and inducing mixed ionic-electronic conductivity in the near-boundary region.