Infrared radiative properties of plasma-sprayed BaZrO3 coatings

The room temperature directional-hemispherical reflectance and transmittance spectra of free-standing atmospheric plasma-sprayed BaZrO3 coatings with different thicknesses were measured in the wavelength range of 0.8–15.0 μm, and the absorption coefficient and scattering coefficient as a function of wavelength were extracted using the modified four-flux model. Results showed that BaZrO3 is a high scattering, low absorption material at the wavelength <6 μm, where turbine engine thermal radiation is most concentrated. The absorption coefficient of BaZrO3 starts to increase rapidly at wavelength of 6 μm, indicating that BaZrO3 is high absorbing and opaque in the long wavelength range. A pronounced absorption peak occurs at a wavelength of 7 μm, and is associated with a BaCO3 coating impurity. The scattering coefficient of BaZrO3 decreases with the increase of wavelength in the whole measured wavelength range, caused by the decrease of the relative size of the scattering center compared with the wavelength.