Impedance studies of an LPG sensor using surface ruthenated tin oxide

A preliminary study of the impedance data as a function of frequency (100 mHz-100 kKz) for pure and surface ruthenated tin oxide with and without LPG indicates the important role of surface states in enhancing the sensitivity of the surface functionalized tin oxide gas sensor. Different types of processes such as diffusion in the pores and electron-transfer due to surface reactions are found to occur at different operating temperatures and the mechanism of hydrocarbon sensing is found to drastically change with temperature in the operational range. For example, the samples at 250 degrees C show diffusion controlled behaviour while those at 350 degrees C predominantly show charge transfer control. The behaviour of these systems are studied with plausible equivalent circuits and a clear distinction has been observed for the surface ruthenated samples, which could be responsible for the enhanced sensitivity at these temperatures. (C) 1999 Elsevier Science S.A. All rights reserved.