Oxidation Prevention
A protective thin film deposit designed to restrict the transport of oxygen atoms to the underlying sensor elements prevents high temperature oxidation and drift. In sensors exposed to exhaust gases or combustion environments, an oxygen barrier layer maintains the chemical composition and electrical resistivity of the sensor elements. This layer is engineered to have extremely low oxygen permeability at elevated temperatures.
By forming a dense atomic network, the material stops the diffusion of oxygen ions, which would otherwise lead to the oxidation of the functional metal layers.
Material Choice
Ceramic oxides such as alumina and silicon dioxide are the primary materials selected for this application because of their low oxygen diffusion coefficients. These materials are deposited via sputtering to form a dense, pinhole free barrier that blocks oxygen pathway networks. The thick ceramic structure resists oxidation even during continuous exposure to high temperature environments.
Functional Integration
Positioned above the sensing grid and below any final protective topcoats, this barrier layer forms a critical component of the multilayer sensor architecture. Sputter parameters must be adjusted to ensure that the oxygen barrier layer is stoichiometric and dense. This density prevents the gas from diffusing through grain boundaries to react with the platinum or palladium strain gauge elements.
Degradation Monitoring
Measurement of the sensor drift rate during long term high temperature testing verifies the sealing performance of this protective deposit. An effective barrier keeps resistance drift within acceptable limits over hundreds of hours of thermal exposure. This testing ensures the stability of the strain measurements in aggressive industrial environments.
