Q & A: IR Coating Designs and Applications

Q. IR sensor optical domes/windows and hypervelocity military aircraft are sample applications that require coatings with extraordinary wear resistance.  What is being done to address this problem?

A. Coating materials and deposition processes have been specially developed to meet this challenge. A few considerations: when depositing durable thin film coatings to surfaces, the chemical composition of the substrates must be considered; an intermediate layer material is often required to initiate strong bonding between substrate and first-coated layer; coating materials used must possess high transmission in the wavelength regions that are transmitted by the substrate; and more.  Other options may include a protective coating, double-sided coating or backside durable AR.

Q. Fluoride compounds as starting materials have properties that are potentially problematic during the production of multi-layer coatings.  Can their performance be improved?

A. Fluoride compounds with known LWIR transparency are constantly being refined in an attempt to improve their evaporation behavior (water affinity, low packing density and tensile stress). Modification of the preparation procedure is being trialed to reduce these effects. For all fluoride compounds, higher substrate temperatures result in higher packing density and thus lower water band depth; low power applied for up to four minutes also drives off adsorbed water. Other techniques are under development. 

Do you have a question about a material for your application? Contact Chris Helwig at christopher.helwig@materion.com.