MICROSTRUCTURE ANALYSIS ON NETWORK-STRUCTURE FORMATION OF SOFC ANODE FROM NiO-SDC COMPOSITE PARTICLES PREPARED BY SPRAY PYROLYSIS TECHNIQUE

The composite particles of NiO and samaria-doped ceria (SDC) having the core-shelf structure and the dispersed structure were synthesized by spray pyrolysis method. The composite particles were sintered at various temperatures onto the electrolyte substrate, and the network-formation process was investigated by scanning electron microscopy (SEM). transmission electron microscopy (TEM), and the electrochemical characterization. In the case of the core-shell type particles, the SDC grains on the surface of the particles began to connect at the first step and the connection between the NiO grains in the neighboring particles started later. On the other hand, it was found that the connection between NiO grains started at almost the same time as that between SDC grains for the dispersed type particles. When the core-shell type composite particles were used, the connections among SDC grains generated and the grain size of NiO inside the particles grew at the initial stages of the sintering, and the densification of the anode was controlled. Therefore. the network-structure having wider connecting necks can be formed after high temperature sintering, and high-performance anode can be obtained. When the dispersed type composite particles are used, electronic conduction paths existed at (lie initial stages of the sintering since the connections among the NiO grains generated oil the Surface of the particles. Furthermore, large triple phase boundaries (TPBs) are obtained due to the well-dispersion of SDC and NiO grains. therefore, the particles have an advantage that high-performance can be obtained by sintering at lower temperatures.