Anna-Lena Larsson

Thin film coatings with variable emittance

The temperature of a nanosatellite in orbit varies strongly as it goes into earth shadow or solar radiation. A variable emittance panel built with an electrochromic material, could improve the temperature control by providing an adaptive thermal control. The active function is due to an electrochromic layer, WO3, deposited by sputtering. Intercalation of Li+ leads to a change in the electron configuration, which modulates the radiation properties. Thin WO3 films were deposited onto Indium Tin Oxide (ITO) coated glass by reactive dc sputtering. IR measurements were done in a Perkin-Elmer 983 spectrophotometer. The IR emittance modulation, (Delta) (epsilon) of WO3 films, deposited on ITO coated glass, has been investigated. The emittance, (epsilon) , is computed from the reflectance, at 25 degrees C. Initial results show emittances in the range from 0.2 to 0.5 crystalline film has (Delta) (epsilon) equals 0.12, and the amorphous film has (Delta) (epsilon) equals 0.3. IR properties of WO3 need to be further investigated as well as the construction of a whole device.

H + Conduction in Solid-State Electrochromic Devices Analyzed by Transient Current Measurements

This paper presents an analysis of transient current measurements on an electrochromic device in order to evaluate the performance of the ion conductor and the average ion mobility in the device. A proton conducting all-thin-film device with WO 3 and hydrated NiO as the working and counter electrodes, respectively, and ZrO 2 as the ion conductor was studied. Potential reversal experiments were performed, and the resulting transient currents were measured and analyzed. The average proton diffusion coefficient for the whole device was found to be of the order of 10 - 1 4 cm 2 /s and the ZrO 2 layer was shown to be the rate-limiting layer.

Infrared optical properties of sputtered WO3

Thin films of amorphous and crystalline tungsten trioxide were deposited onto glass covered with indium tin oxide, by reactive dc magnetron sputtering. The samples were intercalated with Li ions in 1M LiClO4 in propylene carbonate. The infrared reflectance was measured ex-situ at wavelengths between 2 and 50 micrometers for LixWO3 of different thickness, d, and at different Li/W ratios, x. The absorption bands (i.e. the dips in the reflectance spectra) of a thick amorphous film (d equals 1450 nm) get stronger up to the threshold value x equals 0.17. Above this value, the amplitude of the oscillations in the reflectance spectra decreases, which resembles the behavior of a thick crystalline film (d equals 1270 nm). The latter seems to have a lower threshold value, around x equals 0.08 and the spectra at large x are flatter than the ones for the amorphous film.