Wet process-preparation of Re-doped WO3 for wide range of NO2 detection

Abstract

In order to reduce the electric resistance of the WO3 sensing film fabricated from the ion-exchange method, lamellar-structured and Re-doped WO3 was prepared through the acidification method. The mixed solution of Na2WO4 and Re2O7 was dropped into the mixed solution of H2SO4 and HCHO. Then the obtained gel was deposited on alumina substrate with Au electrode for thick film devices and calcined at 300°C. The size of the Re-doped WO3 particles was smaller in one order in magnitude than that of the WO3 by the ion-exchange method. The electric resistance of Re-doped WO3 device in air showed minimum value at the 4 at% Re doping due to the increase in the donor density in the WO3 crystal. As a result, the Re-doped WO3 device exhibited low electric resistance less than 108 Ω even in the 800 ppb NO2. Such a low electric resistance device is suitable for the detection of the wide range of NO2. © 2010 The Ceramic Society of Japan.