Oxygen sensing characteristics of limiting current-type sensors with microstructural and structural variations in diffusion barrier

Several compositional mixtures of Al2O3 (mean diameter = 1.0 mu m)-YSZ (yttria stabilized zirconia, mean diameter= 0.05 mu m) porous layers were used to study the oxygen sensing characteristics and mechanisms of the limiting current-type sensors with various microstructures of the diffusion barriers. The pore size, the porosity, the limiting current, and the degree of the normal diffusion increased with Al2O3 content of the diffusion barrier. A new type of the limiting current-type sensor with a dense layer placed on the top of thin diffusion barrier tape was proposed to get lower operation voltage at a larger pore size and porosity of the diffusion barrier. The limiting current with the proper operation voltage and resolution could be attained easily and reproducibly by varying the microstructure of the diffusion barriers and the structures of the sensors.