Gas Sensor Mixed Layer for Low-Temperature Sensitivity
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Solution Overview
Problem
Conventional gas sensors with oxygen ion conductive solid electrolyte members and noble metal electrodes face challenges in maintaining sensitivity and responsiveness at low temperatures, particularly due to increased gas diffusion resistance and decreased platinum activity.
Innovation Solution
A gas sensor element with a mixed layer of noble metal or noble metal alloy and ZrO2-based ceramic, averaging 800 nm or less in thickness, is formed between the solid electrolyte member and the reference gas-side electrode to reduce oxygen dissociation reaction resistance and prevent gas diffusion obstruction, enhancing sensitivity and responsiveness at low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick intermediate layer (1000 nm) is formed between the solid electrolyte member and the reference gas-side electrode, then oxygen dissociation reaction resistance is reduced, but gas diffusion resistance increases and sensor output and responsiveness decrease at low temperature
Solution Approach 1:
The patent changes the critical parameter of intermediate layer thickness from conventional 1000 nm to 100 nm or less (preferably 50 nm or less). This parameter change simultaneously achieves low oxygen dissociation reaction resistance while maintaining gas diffusion permeability, enabling high sensor output and responsiveness at low temperatures (200-300°C) without the trade-off present in conventional designs.
Solution Approach 2:
The patent employs composite material structure by forming the intermediate layer from a mixture of noble metal particles (Pt, Pd, Au) and ZrO2-based ceramic particles. This composite structure provides both the catalytic activity for oxygen dissociation (reducing reaction resistance) and the porous structure for gas diffusion, resolving the contradiction between reaction efficiency and mass transport.
2Productivity
If platinum layers are formed on the surfaces of cermet electrodes by electrolytic plating, then specific surface area of platinum increases and reaction rate improves, but sensor output and responsiveness decrease at low temperature due to decreased platinum activity
Solution Approach 1:
The patent introduces an intermediate layer as a mediator between the solid electrolyte member and the reference gas-side electrode. This intermediate layer, composed of noble metal particles mixed with ZrO2-based ceramic particles, serves as an active layer that enhances oxygen dissociation reaction at low temperatures while maintaining gas diffusion, thereby improving sensor output and responsiveness without relying solely on platinum layer surface area.
3Reliability
If the gas sensor element is heated by the heater to a predetermined temperature, then sufficient sensor output is obtained, but power consumption increases and fuel consumption increases
Solution Approach 1:
The patent changes the operational temperature parameter by enabling the sensor to achieve high output and responsiveness at low temperatures (200-300°C) through the ultrathin intermediate layer structure. This eliminates the need for high-temperature heating operations, thereby significantly reducing power consumption and fuel consumption while maintaining sufficient sensor output for accurate exhaust gas composition detection.
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 gas sensor element achieves high sensitivity and responsiveness at low temperatures (200-300°C) with reduced variation in performance, contributing to fuel and power saving by maintaining effective sensor output and responsiveness.
Implementation Method 1
a solid electrolyte member made of an oxygen ion conductive ZrO2-based ceramic
Implementation Method 2
the mixed layer contributes to reducing oxygen dissociation reaction resistance
Implementation Method 3
since the average thickness of the mixed layer is 800 nm or less, gas diffusion resistance is prevented from increasing
Data Source
AI summary
A gas sensor element having good sensitivity and responsiveness at low temperature, and a gas sensor are provided. The gas sensor element includes a solid electrolyte member made of an oxygen ion conductive ZrO2-based ceramic, and a reference gas-side electrode and a measuring gas-side electrode respectively provided on a surface and the other surface of the solid electrolyte member. The gas sensor includes the gas sensor element. The reference gas-side electrode and the measuring gas-side electrode are formed so as to face each other with the solid electrolyte member interposed therebetween, and are both made of a noble metal or a noble metal alloy. A mixed layer with an average thickness of 800 nm or less is formed between the solid electrolyte member and the reference gas-side electrode. The mixed layer contains a noble metal or a noble metal alloy and a ZrO2-based ceramic mixed with each other.