THE ELECTROCHROMIC PROPERTIES AND MECHANISM OF HXWO3 AND LIXWO3

The concentration of hydrogen and lithium ions in colored and bleached WO3 films was measured by secondary ion mass spectroscopy (SIMS) depth profile analysis and inductively coupled plasma mass spectroscopy. X-ray analysis revealed that as-prepared WO3 films changed to a mixture of WO3 and tungsten bronze (HxWO3 or LixWO3) during the electrical coloration process. Poly-AMPS, 10% H2SO4 aqueous solution, and 1M LiClO4-propylene carbonate (PC) were used as the electrolytes. The crystal structure of colored films changed back to the initial state when the films were bleached, even though a large quantity of hydrogen or lithium atoms still remained inside bleached films. We proposed that a fraction of hydrogen or lithium cations will bind on optically inactive sites, possibly the grain boundaries of the WO3 polycrystalline film in the bleaching process, and will not contribute to the coloration. © 1990.