Coupled microstructural and transport effects in n-type sensor response modeling for thin layers

The chemical gas sensor system of CO detection in a SnO2 matrix was considered. A model was formulated which incorporated the coupled processes of gases diffusing into a porous ceramic and then participating in surface chemical reactions of adsorption, ionization and desorption. Microstructural properties of the sensor matrix were coupled with the diffusion and surface chemistry processes. The consequent surface chemical state served to partition bulk and grain boundary contributions to the n-type material conductance. Conductivity levels determined both with and without the presence of the target gas, CO, allowed sensor response to be determined as a function of film thickness.This simulation represents a modeling advance as it is the first to couple spatial variation of microstructural properties with diffusing gas species and the attendant surface chemistry and electroceramic properties, to predict sensor response as a function of film thickness. This will serve to be a useful design tool for ensuing materials research work towards improved sensor device development.