Type of presentation: Poster

MS-14-P-3348 Imaging and Spectroscopy of Filler-Matrix Interaction in a Ceramic Nanocomposite: First Evidence

GULGUN M. A.¹, SHAWUTI S.¹, CEH M.^1,2, STURM S.^1,2

¹SABANCI UNIVERSITY FENS AND SUNUM, ²JOSEF STEFAN INSTITUTE

m-gulgun@sabanciuniv.edu

An inorganic salt (Na2CO3)-oxide nanoparticles (samarium doped ceria, SDC, (Sm0.2 Ce0.8O1.9)) composite showed an unexpected sinergy in electrical behavior [1-3]. The ionic conductivity of the composite shows a marked increase as the average oxide particle size decreases and when the oxide particle to matrix salt ratio is tailored to an optimum value (Figure 1) [4]. It was suggested that the interfacial interaction of oxide nanoparticles with the amorphous carbonate salt matrix would enhance the conductivity by generating new pathways for ionic transport.
High resolution transmission electron microscopy and energy filtered imaging was utilized to investigate the extend and type of this interfacial phenomenon. A TEM bright field image of the nanocomposite is shown in Figure 2a. Energy filtered imaging provided the first evidence for the influence of oxide surface on the structure of solid amorphous salts in the interfacial region. The interaction may not only create a new pathway fort he conduction but also increase the mobility of the conducting ion complexes. By altering the surface properties of the oxide nanoparticles it is possible to control the extend of this interaction.
An JEOL ARM 200 CFEG STEM and GATAN Quantum 965 ER Spectrometer were utilized to investigate the interaction between the oxide surface and the amorphous carbinate matrix phase. Energy filtered imaging of the composite using C_K, Na_ K, Sm_ L and Ce_L edges with a three window method proved to be problematic since Na-K (1074 eV) line and Sm_L (1075 eV) line are only 1 eV away from each other. However, the Ce_L and C_K line images are useful to visualize the carbonate shell around the ceria particles (Figure 2 b and c).

[1] B.Zhu, J.Power sources, 93 (2001) 82.
[2] B.Zhu, J. Power sources, 114 (2003) 1.
[3] B. Zhu, X. Liu, M. Sun, S.J, J. Solid State Sci., 8 (2003) 1127.
[4] S. Shawuti and M. A. Gulgun, 'Solid Oxide-Molten Carbonate Nano-composite Fuel Cells: Particle Size Effect', in review for J. Power Sources, 2014 Jan.

Fig. 1: Figure 1. The Nyquist plot for nanocomposites with different average particle sizes (PS) taken at 350°C, showing that the impedance of the composites increase with increasing PS.	Fig. 2: Figure 2 a. TEM bright field image of the SDC – Na2CO3 nanocomposite electrolyte. The light grey areas between the SDC oxide particles are the amorphous carbonate matrix.
Fig. 3: Figure 2 b. Energy filtered image taken Ce_M line showing the oxide particle locations clearly.	Fig. 4: Figure 2 c. Energy filtered image taken C_K line showing the concentration of carbonte ion clearly.