Quantitative evaluation of pore structure effects on thermal conductivity of SDC functional layer for IT-SOFCs: experimental investigation and three-layer model prediction

Porous structures are widely utilized in the functional layers of solid oxide fuel cells (SOFCs), in which thermal conductivity plays a critical role in thermal management and structural stability. In this work, samarium-doped ceria (Ce 0.8 Sm 0.2 O 1.9 , SDC) was selected as the matrix material, with carbon powder as a pore former, to systematically investigate the evolution of thermal conductivity under varying porosity and temperature conditions. Microstructural characterization revealed a distinct sintering-induced sandwich-like stratification at low pore-former contents, which significantly influenced the heat transport behavior. To capture this unique microstructural feature, a theoretical heat conduction model was developed. This proposed model comprehensively accounts for porosity, structural non-uniformity, and temperature, enabling the quantitative prediction of the effective thermal conductivity of porous SDC functional layers. The model predictions exhibit excellent agreement with experimental results, with a mean relative error (MRE) of 4.16% and a determination coefficient (R²) greater than 0.98. This study establishes a reliable and physically grounded approach for predicting the thermal conductivity of porous functional layers, providing theoretical guidance for the optimization of thermal performance and structural design of materials for intermediate-temperature SOFCs (IT-SOFCs).