High-Temperature Sensor Coating to Block Drift-Causing Diffusion
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Solution Overview
Problem
High-temperature temperature sensors used in the automotive industry to measure exhaust gas and combustion temperatures experience drift due to diffusion of foreign atoms like chromium, nickel, and silicon into the resistance structure, leading to inaccurate readings.
Innovation Solution
A high-temperature sensor with a zirconium oxide or zirconium oxide ceramic substrate, coated with a metal oxide insulation layer and a ceramic intermediate layer, featuring openings that expose the substrate surface to prevent foreign atom diffusion, and a protective layer to create a diffusion barrier, along with a platinum resistance structure and terminal contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a complete insulation layer covers the substrate, then electrical insulation is improved, but foreign atom diffusion into the resistance structure increases
Solution Approach 1:
The insulation layer is segmented by forming openings (through-holes or recesses) that expose portions of the substrate surface. This segmentation allows the insulation layer to provide electrical insulation where needed while creating diffusion barrier pathways through the openings filled with diffusion barrier material, thus resolving the contradiction between maintaining insulation and preventing foreign atom diffusion.
Solution Approach 2:
A diffusion barrier material is introduced as an intermediary substance filling the openings in the insulation layer. This intermediary material specifically blocks foreign atom diffusion pathways while allowing the insulation layer to maintain its electrical insulation function in the surrounding areas, thus resolving the contradiction between insulation and diffusion prevention.
2Measurement precision
If the insulation layer is made porous to allow exhaust gas flow, then measurement accuracy is improved, but foreign atom diffusion into the resistance structure increases
Solution Approach 1:
The insulation layer is segmented into insulating regions and opening regions. The openings provide pathways for exhaust gas flow to reach the resistance structure for accurate temperature measurement, while the filled diffusion barrier material in the openings prevents foreign atom diffusion, thus resolving the contradiction between measurement precision and diffusion prevention.
Solution Approach 2:
Different regions of the sensor structure are assigned different properties: the insulation layer provides electrical insulation in covered areas, while the openings filled with diffusion barrier material provide diffusion protection. The resistance structure in areas accessible through openings enables temperature measurement. This local differentiation of functions resolves the contradiction between allowing gas flow for measurement and preventing diffusion.
3Object-affected harmful factors
If a thick diffusion barrier layer is applied, then foreign atom diffusion is prevented, but sensor complexity and manufacturing difficulty increase
Solution Approach 1:
Instead of applying a thick diffusion barrier layer across the entire substrate surface, the diffusion barrier material is segmented and placed only in the openings of the insulation layer. This segmented approach provides effective diffusion protection through targeted placement while reducing overall material usage and simplifying the layer structure compared to a complete thick barrier layer.
Solution Approach 2:
Rather than providing complete coverage with a thick diffusion barrier layer (excessive action), the invention uses partial coverage by filling only the openings in the insulation layer with diffusion barrier material. This partial action is sufficient to prevent foreign atom diffusion pathways while reducing manufacturing complexity and material requirements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design minimizes sensor drift by preventing foreign atom diffusion into the resistance structure, maintaining accuracy and stability even in corrosive exhaust gas environments.
Implementation Method 1
the diffusion of foreign atoms, such as chromium, nickel, iron, and silicon, from the exhaust gas flow into the resistance structure
Implementation Method 2
a protective layer and/or a cover is arranged on the ceramic intermediate layer, in which at least one opening is formed in the insulation layer
Data Source
AI summary
One aspect relates to a high-temperature sensor, having a coated substrate. The substrate contains a zirconium oxide or a zirconium oxide ceramic, at least one resistance structure and at least two connection contacts. The connection contacts electrically contact the resistance structure. The substrate is coated with an insulation layer. The insulation layer contains a metal oxide layer, the resistance structure and the free regions of the insulation layer, on which no resistance structure is arranged, are coated at least in regions with a ceramic intermediate layer, and a protective layer and/or a cover is arranged on the ceramic intermediate layer. At least one opening is formed in the insulation layer, which exposes at least sections of a surface of the substrate.