Preparation of hollandite-type KxGaxSn8−xO16 thin film and NO adsorption behavior

Thin films of hollandite-type KxGaxSn8−xO16 (KGSO) were fabricated on YSZ substrate by spin-coating method. Those are colorless and transparent, and about 100–150 nm thick at minimum, consisting of KGSO primary particles with about 20 nm in average size. The adsorption behavior of NO on the thin film was examined by diffuse reflectance infrared fourier transform spectroscopy and temperature programmed desorption method. The sample was preheated at 973 K in a mixture gas of N2 and O2 prior to NO adsorption. As the oxygen ratio in the mixture gas increased up to 40%, absorption bands appeared and got stronger an around 1400 cm−1, and the amount of desorption in the range from 650 to 850 K increased. Those bands were assigned to NO2 species in the chelating and nitrito form, respectively, referring to the literature about NO on La2O3. The amount of desorption was equal to the number of tunnel end face per unit cell. It was found that the coexistence of oxygen remarkably improves the adsorption ability of NO on KGSO thin films.