23 August 1995 Optical constants of V1-xWxO2 thermochromic films and their application to the selective radiating material
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Tungsten doped vanadium oxide (V1-xWxO2) films are known to be reliable thermochromic materials for their semiconductor/metal transition temperature which can be controlled by the doping level x. In this paper, firstly, the optical constants of V1-xWxO2 films on glass substrate were determined from the reflectance spectra and the transmittance spectra measured at 25 degree(s)C and 80 degree(s)C in the wavelength region from 300 to 2500 nm. In the determination we used Drude model in the high temperature metallic-phase and the least square method in the low temperature semiconductor-phase. The calculated reflectance spectra and the transmittance spectra using the Drude model with adequate values of the parameters are consistent with the measured ones in whole spectral region in the high temperature phase. Secondarily, we carried out a simulation of radiative cooling power of some selective radiating materials whose substrates were V1-xWxO2 films, using the optical constants in IR region obtained by the extrapolation of the obtained ones in visible and near IR region. As the high temperature phase of V1-xWxO2 has high reflectivity, we can use this thermochromic film as a substrate of the selective radiating material which consists of an adequate film on a high reflective substrate. The simulation shows the capability of automatic temperature control of the radiative cooling system tandemed by SiO film, V1-xWxO2 film, and the black substrate by different doping level x.
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Masato Tazawa, Masato Tazawa, Ping Jin, Ping Jin, Sakae Tanemura, Sakae Tanemura, } "Optical constants of V1-xWxO2 thermochromic films and their application to the selective radiating material", Proc. SPIE 2531, Optical Materials Technology for Energy Efficiency and Solar Energy Conversion XIV, (23 August 1995); doi: 10.1117/12.217341; https://doi.org/10.1117/12.217341

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