Structured ceramic elements are often used in chemical engineering processes for optimization or increasing the efficiency of technical equipment. Knowledge of the thermal properties, including heat conduction and thermal radiation effects, of these elements is necessary for designing high temperature applications. Well-known elements are honeycombs or packed beds. These have recently been substituted by sponges (open-cell foams) due to several advantageous properties. Regarding this material, only a few, but not sufficient, investigations on radiative heat transfer exist in the literature to date. In this publication, experimental results for the spectral transmittance and reflectance obtained by Fourier transform infrared spectrometry (FTIR) for different ceramic sponges (variations of material, porosity and cell density) are presented. Within these parameters, the total extinction coefficient (here: Rosseland extinction coefficient) and the total emissivity of the different sponges investigated are determined. The total extinction coefficient reveals a strong dependency on cell size and porosity while the total emissivity only depends on porosity. These optical parameters allow the estimation of radiative heat transfer in ceramic sponges. Furthermore, an empirical correlation for predicting the total extinction coefficient from the window diameter is proposed. The radiative part of the thermal conductivity of ceramic sponges can be estimated using the Rosseland extinction coefficients obtained. (C) 2014 Elsevier Ltd. All rights reserved.