Optical properties of an all-plastic WO3•H2O-based infrared modulator

WO3.H2O powder embedded in a plastic matrix has demonstrated attractive properties as a flexible emissivity modulator driven by the electrochemical insertion of lithium. The near infrared optical properties of LixWO3.H2O are investigated as a function of the lithium intercalation level x for 0less than or equal toxless than or equal to2.65. The reflectivity at 2.5 mum, measured through a glass window, was found to vary between 0.15 and 0.4 over the alpha intercalation phase (0less than or equal tox<0.3), i.e., demonstrating an emissivity contrast of similar to0.25. For xgreater than or equal to0.1 the LixWO3.H2O-based plastic device exhibits a Drude behavior comparable to that of monoclinic tungsten oxide (m-WO3) thin films. For larger intercalation levels, the performances are affected by some irreversible structural modifications of the LixWO3.H2O lattice. (C) 2004 American Institute of Physics.