Non-destructive Gas Sensor Electrode Inspection via Impedance Calibration
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Solution Overview
Problem
Existing methods for inspecting the Au maldistribution degree on noble metal particle surfaces in gas sensor electrodes are destructive and inefficient, making them unsuitable for mass production.
Innovation Solution
A non-destructive inspection method using a calibration curve to correlate the Au maldistribution degree with alternative indices such as direct-current resistance or reaction resistance, allowing for faster evaluation without the need for XPS or AES analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If XPS analysis or AES analysis is performed to evaluate Au abundance ratio, then measurement precision is improved, but the sensor element must be exposed or broken making it destructive and unsuitable for mass production
Solution Approach 1:
The patent introduces an intermediary measurement approach by using electrochemical impedance spectroscopy (EIS) as a mediator to indirectly evaluate the Au abundance ratio. Instead of directly analyzing the electrode surface requiring exposure or breaking, the method measures electrical impedance characteristics that correlate with Au distribution, enabling non-destructive assessment suitable for mass production while maintaining evaluation capability
Solution Approach 2:
The patent replaces the mechanical/physical destruction method (peeling or breaking the sensor element to expose the electrode) with an electrical measurement method. By substituting the mechanical exposure process with electrochemical impedance spectroscopy, the invention eliminates the need for destructive sampling while still obtaining Au abundance ratio information
2Measurement precision
If the surface protective layer is peeled or the sensor element is broken to expose the sensing electrode, then Au abundance ratio can be measured, but the inspection process becomes destructive and time-consuming
Solution Approach 1:
The patent uses electrochemical impedance spectroscopy as an intermediary method to measure Au maldistribution degree without direct exposure. The EIS technique measures electrical impedance at different frequencies, and the characteristics of these measurements serve as intermediaries that correlate with Au distribution, eliminating the need for time-consuming exposure or breaking processes
Solution Approach 2:
The patent changes the measurement parameter from direct surface composition analysis (requiring exposure) to electrical impedance characteristics. By measuring impedance at multiple frequencies and analyzing the relationship between frequency response and Au distribution, the method achieves rapid non-destructive inspection while maintaining measurement accuracy
3Productivity
If non-destructive inspection method is used, then productivity is improved by enabling 100% inspection, but measurement precision may be compromised without direct electrode exposure
Solution Approach 1:
The patent establishes a feedback relationship between electrochemical impedance measurements and Au maldistribution degree. By measuring impedance at multiple frequencies and using the relationship between frequency response characteristics and known Au distribution patterns, the system can accurately determine Au maldistribution degree non-destructively, enabling 100% inspection without sacrificing measurement precision
Solution Approach 2:
The patent performs preliminary calibration to establish the relationship between electrochemical impedance characteristics and Au abundance ratio before actual inspection. This preliminary action creates a reference framework that allows subsequent non-destructive measurements to achieve accurate Au maldistribution degree evaluation, combining high productivity with maintained precision
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
Enables fast and non-destructive inspection of Au maldistribution degree, ensuring consistency in sensor element production and improving the sensitivity of gas sensors.
Implementation Method 1
the gas sensor element heated to a predetermined temperature by the heater
Implementation Method 2
a value of direct-current resistance between the inspection target electrode and the reference electrode or a value of direct current flowing between the inspection target electrode and the reference electrode
Data Source
AI summary
A method of inspecting an electrode provided in a gas sensor element includes the steps of: producing, in advance, a calibration curve representing a relation between an Au maldistribution degree defined based on a ratio of an area of a portion at which Au is exposed on a noble metal particle surface and calculated from a result of XPS or AES analysis on an inspection target electrode, and a predetermined alternative maldistribution degree index correlated with the Au maldistribution degree and acquired in a non-destructive manner from the gas sensor element heated to a predetermined temperature; acquiring a value of the alternative maldistribution degree index for the inspection target electrode of the gas sensor element while the gas sensor element is heated to the predetermined temperature; and determining whether the Au maldistribution degree satisfies a predetermined standard based on the calibration curve and the acquired inspection value.