Absorbers for concentrating solar power plants require materials that are resistant to high temperatures and spectrally selective, i.e., highly absorbent in the visible and near infrared range and low-emissive in the infrared range. To improve the absorbing power of the receivers in concentrating solar power plants, an optical end coating based on tantalum oxynitride can be deposited on an absorbing bilayer based on metal and ceramic materials. Antireflective Ta O x N y coating can maximize the transmission of solar radiation to the W/W-SiCH bilayer absorber material which has been previously studied and ensure a good thermomechanical resistance of the whole coating. For this study, Ta O x N y are deposited by reactive sputtering technique. Their chemical composition is investigated by Ion Beam Analysis which shows compositions ranging from tantalum oxide to tantalum nitride depending of the gas flow rate. Optical properties are determined by ellipsometry and UV-Visible spectroscopy. The microstructure determined by the Pair Distribution Function (PDF) reveals a mixture of TaN, TaON and Ta 2 O 5 phases.