Role of microstructure on the electrical properties of ceria-based composites

This work investigates the preparation and characterization of composite membranes for high-temperature CO 2 separation. Materials were prepared using Gd-doped ceria (CGO) and a eutectic mixture of Na 2 CO 3 and Li 2 CO 3 (NLC) as ceramic and molten phases, respectively. Membranes were obtained through a two-step process: initial consolidation of the ceramic phase followed by impregnation with molten carbonates. Various processing conditions were optimized to achieve homogeneous and strong ceramic skeletons using organic pore-forming agents and sintering aids. Sintering schedules were chosen with respect to each processing condition, namely 1400 °C and 900 °C for materials with organic agent and sintering aids, respectively. Consolidated skeletons and resulting membranes were similar in densification (≈70 % and ≈95 %, respectively). Comparable impedance spectroscopy in air and in a CO 2 -rich atmosphere showed no meaningful change in bulk other than a slight change in conductivity at temperatures above the melting point of salts (500 °C). The ambipolar conductivity and tortuosity analysis provides insights into the behavior of both the isolated ceramic phase and the composite, facilitating an understanding of the microstructural effect on the selected materials. • Distinct microstructural designs of Gd-doped ceria impregnated with (Na 0.48 , Li 0.52 ) 2 CO 3 membranes. • Higher conductivity and lower tortuosity in membranes with skeletons obtained via sintering aid vs. organic pore formers. • Conductivity of membranes in air and in CO 2 + air atmosphere. • Consideration on the effect of microstructure on ambipolar conductivity.