Gas Sensor Element With Porous Connection Reducing Nernstian Force

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Solution Overview

Problem

Existing gas sensors face accuracy deterioration due to the generation of Nernstian electromotive force at the three-phase interface between the peripheral-face conducting section, the solid electrolyte body, and external gases, especially when the size of the three-phase interface is large.

Innovation Solution

The sensor element incorporates a conducting section with a gas-permeable connection portion and a contact area of 1.10 mm2 or smaller between the connection portion and the solid electrolyte body, reducing the increase in Nernstian electromotive force.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the peripheral-face conducting section is made with larger size to improve electrical connection, then the electrical conductivity is improved, but the Nernstian electromotive force increases causing accuracy deterioration

Engineering Contradiction:

Improveelectrical connection reliabilityVSAvoidgas concentration detection accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent applies local quality by creating a gas-permeable connection portion with specific local properties (porosity) at the interface between the conducting section and solid electrolyte body. This localized modification allows gas passage while maintaining electrical connection, preventing the formation of a large three-phase interface that would generate Nernstian electromotive force, thus resolving the contradiction between electrical connection reliability and detection accuracy.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent utilizes porous materials by forming a connection portion with porosity in the conducting section. This porous structure allows external gas to pass through to the solid electrolyte body while maintaining electrical conductivity. The porous connection portion prevents the formation of a large three-phase interface, thereby reducing Nernstian electromotive force and maintaining detection accuracy while ensuring reliable electrical connection.

Inventive Principle:

Principle #31Porous materials

2Measurement precision

If the contact area between the conducting section and solid electrolyte body is reduced to minimize three-phase interface, then the Nernstian electromotive force is reduced, but the electrical connection stability deteriorates

Engineering Contradiction:

Improvegas concentration detection accuracyVSAvoidelectrical connection stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent applies parameter changes by controlling the contact area between the connection portion and solid electrolyte body to be within a specific range (0.01 mm² to 1.10 mm²). This parameter optimization ensures sufficient electrical connection stability while minimizing the three-phase interface area that would generate Nernstian electromotive force, thereby resolving the contradiction between connection stability and detection accuracy.

Inventive Principle:

Principle #35Parameter changes

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

This configuration effectively reduces the likelihood of accuracy deterioration in detecting the concentration of specific gases by minimizing the Nernstian electromotive force, as demonstrated through experiments and analyses.

Implementation Method 1

an element body including an oxygen-ion-conductive solid electrolyte body

Methodology Applied

Scientific EffectOxygen-ion conduction: Fast Ion Conductor

Implementation Method 2

a connection portion in the outer conducting section to the inner conducting section is gas permeable

Methodology Applied

Scientific EffectGas permeation: Permeation

Implementation Method 3

Nernstian electromotive force may be generated at the three-phase interface between the peripheral-face conducting section, the solid electrolyte body and the gas

Methodology Applied

Scientific EffectNernst effect: Nernst Effect

Data Source

PatentUS20250164438A1Sensor element and gas sensor

Publication Date: 2025.05.22 NGK INSULATORS LTD

AI summary

A sensor element configured to detect a concentration of a specific gas in a measurement-object gas, the sensor element includes an element body having a front end, a rear end and a peripheral face; an inner electrode disposed inside the element body; and a conducting section including an inner conducting section and an outer conducting section, the outer conducting section disposed at the peripheral face and including a connector electrode disposed at a part of the peripheral face that is near the rear end, the outer conducting section being electrically continuous with the inner conducting section. A connection portion in the outer conducting section to the inner conducting section is gas permeable, and a contact area between the connection portion and the solid electrolyte body is 1.10 mm2 or smaller.