Bulg. J. Phys. vol.19 no.3-4 (1992), pp. 041-048

High-Temperature Stability of the Optical Properties of Chloride Black Molybdenum Solar Selective Surfaces

K.A. Gesheva
Central Laboratory for Solar Energy and New Energy Sources, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria
Abstract. Black molybdenum films, deposited by pyrolytical hydrogen reduction of MoO2Cl2 in temperature range 550–710°C have been tested in vacuum (0.1 Torr) at 500°C and in air at 350°C for a long time. Films as deposited were studied by measuring their reflectance in the solar spectrum range (0.3–2.4 μm) and in the infrared range (IR) (2.5–15 μm). Before testing films were precoated with a protective and at the same time antireflective Si3N4 coating. Optical measurements are made for Si3N4-coated films, too. During the test, films were periodically taken out from the furnace for optical measurements. Surface defects of the films before and during the test were also under control by optical microscope observation.

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