Au-Gradient Sensor Electrode for Stable NOx Gas Detection
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Solution Overview
Problem
Existing gas sensors experience a deterioration in detection accuracy over time due to the deposition of Au from the pump electrode to the sensor electrode, leading to a decrease in output sensitivity and accuracy for specific gas components like NOX.
Innovation Solution
The gas sensor is designed with a sensor electrode containing Au in a surface layer with a specific distribution, where the Au content in the surface layer is greater than in the reference layer, preventing Au from easily moving to the surface during use, thereby maintaining detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Au is added to the sensor electrode to improve detection accuracy, then detection accuracy is improved, but Au deposits from the pump electrode to the sensor electrode over time, causing output sensitivity to decrease
Solution Approach 1:
The patent applies local quality by creating a specific Au concentration distribution within the sensor electrode, where the surface layer (0-0.3μm depth) contains 0.03-3 mass% Au and the inner layer (0.3-3μm depth) contains 0.3-10 mass% Au. This non-uniform distribution allows the surface to maintain detection accuracy while the inner layer provides Au reservoir to prevent sensitivity degradation over time.
Solution Approach 2:
The patent implements preliminary action by pre-establishing the optimized Au concentration gradient during sensor electrode fabrication. The surface layer is designed with lower Au content (0.03-3 mass%) to maintain detection accuracy, while the inner layer contains higher Au content (0.3-10 mass%) that can slowly diffuse outward over time, preemptively compensating for Au loss from the pump electrode and maintaining stable output sensitivity throughout the sensor's operational life.
2Reliability
If Au content in the sensor electrode is increased to prevent output decrease, then reliability is improved, but detection accuracy deteriorates due to excessive Au deposition on the surface
Solution Approach 1:
The patent resolves this contradiction by implementing local quality with a stratified Au concentration distribution. The surface layer (0-0.3μm) maintains low Au content (0.03-3 mass%) to preserve detection accuracy, while the inner layer (0.3-3μm) contains higher Au content (0.3-10 mass%) to provide long-term stability. This spatial differentiation allows each layer to fulfill its specific function without compromising the other.
Solution Approach 2:
The patent applies dimensionality change by transitioning from a uniform Au distribution to a depth-dependent concentration gradient. By controlling Au content as a function of depth from the surface, the patent creates a three-dimensional composition profile that simultaneously optimizes both surface detection performance and bulk stability properties.
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 sensor maintains high detection accuracy for specific gas components over an extended period by ensuring the Au content in the surface layer remains higher than in the reference layer, reducing the output decrease rate and preserving sensitivity.
Implementation Method 1
a solid electrolyte that has ion conductivity
Implementation Method 2
a sensor electrode that is provided on a surface of the solid electrolyte in a state in which the sensor electrode is housed inside the gas chamber
Data Source
AI summary
A gas sensor includes a sensor element including a solid electrolyte, a gas chamber, a pump electrode, a sensor electrode, and a reference electrode. The pump electrode and sensor electrode are provided in the solid electrolyte in a state in which the pump electrode and the sensor electrode are housed in the gas chamber. The reference electrode is provided in the solid electrolyte. The pump electrode and the sensor electrode contain Au. Au content in a surface layer is equal to or greater than 1 mass % and higher than Au content in a reference layer. The surface layer is an area from a surface of the sensor electrode to a depth of 0.3 nanometers. The reference layer is an area located at depths ranging from 2 or more to 3 or less nanometers beneath the surface of the sensor electrode.