Variable Emittance Devices

The development of thin film devices and coatings with an electrically tunable emittance in the 3-5 microns and 8-12 microns spectral bands in proposed. The emittance modulation is based on reversible electrochromic switching in thin films of crystalline transition metal oxides. On electrochemical reduction, these oxides undergo a broadband IR optical transition between that of a wide band gap, transparent semiconductor and a reflective metal. Electrochromic device structures are proposed which allow these oxides to be electrically switched in a continuously adjustable manner between low and high emittance states in reposnse to a low voltage DC signal. Innovation in the use of materials that combine electrical conductivity with either high infrared transmittance or absorptance (emittance) and allow the fabrication of flexible device structures are described. The objective of the Phase I effort is to fabricate and characterize prototype variable emittance devices embodying the innovations proposed. The Phase II effort would expand the base of materials and device designs with the objective of optimizing emittance switching in structures suitable for applications on military platforms.