Experimental and numerical study on structural and thermal radiation properties of yttrium oxide sputtered on sapphire

Materials for infrared domes are required to maintain good properties in harsh environments including mechanical strength, optical transmittance over a wide range of wavelengths and low emissivity. The purpose of this work is to sputter Y2O3 film onto a sapphire substrate by a radio frequency magnetron sputtering method and investigate the structural and thermal radiation properties of the films. In addition, the apparent emissivity of the coated sapphire is simulated for different film thicknesses at different temperatures. The experimental results show that the surface of the Y2O3 film is homogeneous, has a dense morphology and is totally polycrystalline. After being coated with the Y2O3 film, the transmission of the sapphire substrate is improved and the emissivity is decreased with increasing film thickness, especially at high temperatures. Simulation results show that apparent emissivity of a sapphire substrate at high temperatures can be reduced effectively by the Y2O3 film when the ratio of the thickness of Y2O3 film and sapphire substrate is larger than 0.01.