Infrared radiative properties of 8-mol%-yttria-stabilized zirconia (8YSZ) ceramics of porosity 3% as applied as electrolyte for solid oxide fuel cells (SOFCs) were studied at room and elevated temperatures in the wavelength range from 2 to 20 mu m. The room-temperature directional-hemispherical measurements of reflectance and transmittance for thin samples were combined with normal emittance measurements at several temperatures up to 1700 K. The use of the radiation transfer theory in a region of semi-transparency enabled identification of absorption and scattering properties of the material. Both a detailed numerical procedure using the known discrete ordinates method and a novel iterative analytical solution were employed. An analysis based on the Mie theory confirms volumetric scattering by sub-micron size polydisperse pores in the ceramics. It is shown that the absorption coefficient of 8YSZ increases considerably with temperature. This effect should be taken into account in combined heat transfer calculations for SOFCs.