Influence of crystallinity on CO gas sensing for TiO2 films

In the present research, carbon monoxide (CO) gas sensing response was studied for TiO2 thick films calcined and sintered between 700 and 900 °C. Crystalline phase, crystallite size, surface area, particle size, and amorphous content were measured for the calcined powder. Crystallinity of the powder was found to affect sensing response significantly towards CO. Anatase phase of TiO2 thick film was stable up to 900 °C however, as calcination temperature increased from 700 to 900 °C, surface area and amorphous phase content decreased. Films calcined and sintered at 700 °C showed a lower response towards CO than those calcined at 800 °C. Upon increasing the calcination temperature further, particle growth and reduced surface area hindered the sensing response. A calcination temperature of 800 °C was necessary to achieve sufficient order in the crystal structure leading to more efficient adsorption and desorption of oxygen ions on the surface of TiO2.