Abstract

Certain compounds of polyvalent metals exhibit coloration which depends on the oxidation state of their cations. The best known "chromogenic” materials are tungsten trioxide WO₃ forming deep blue alkali and hydrogen tungsten bronzes M_XWO₃ on reduction. Thin-layer systems whose transmittance or reflectance can be varied reversibly and continuously by an electric voltage or by other methods are of great interest for many applications. However, a large-scale progress of such devices has not yet been achieved. One of the main reason of this state is a serious lack of data on chromogenic materials as function of their oxidation state and energy level structure. Such situation often causes misunderstanding of the exact processes during coloration.

© 1996 IEEE