Effect of Precious Metal Catalyst on TiO ₂ Thickfilm HEGO Sensor with Multi-Layer Alumina Substrate

The basic characteristics of the TiO₂ sensor were introduced on a previous SAE paper which was submitted by NGK Spark Plug Co., Ltd. and further discussed on several other papers which have also been recently published. This paper will describe the effect of a precious metal catalyst on vehicle emissions. Emphasis is placed on the effect of the distribution of the precious metal catalyst in the titania element which significantly affects the reaction among unburned components in the exhaust gas as well as sensor performance.

The relationship between the catalyst distribution in the sensor element, and the closed loop emission results, including test variability, will also be discussed in this paper.