Influence of particle size on the conductance of SnO2 thick films

The electrical response of SnO2 thick films was found to be highly dependent on the grain size. This result can be explained as the consequence of the type of intergranular potential barriers developed at intergrains. Specifically, samples with smaller particle size have overlapped potential barriers and samples with higher particle size have separated potential barriers. Also, the influence of gas transport phenomena on the resistance of the gas sensor was investigated. From an analysis of the possible mechanisms involved in the oxygen diffusion, the Knudsen diffusion is suggested as the controlling step.