Limiting-Current Gas Sensor Insulating Film Reduces Surface Conduction
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Solution Overview
Problem
Conventional humidity sensors face challenges such as low measurement accuracy in low-humidity regions, high temperature dependency, and durability issues, particularly in environments with condensation or high temperatures, and existing zirconia-based sensors have high power consumption and limited industrial applications.
Innovation Solution
A limiting-current type gas sensor is developed with a substrate, porous lower and upper electrodes, and a solid electrolyte layer, where an insulating film creates non-contact between the edge face of the solid electrolyte layer and the lower electrode, reducing surface-conduction current and enabling low power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If zirconia solid electrolyte is used for high-temperature humidity measurement, then measurement reliability is improved, but power consumption increases to 100 W
Solution Approach 1:
The patent changes the operating temperature parameter from hundreds of degrees Celsius to 150°C or lower, and modifies the electrolyte composition to include zirconia with specific additives (ceria, alumina, silica) in controlled ratios, enabling reliable humidity measurement at reduced power consumption
Solution Approach 2:
The patent uses composite electrolyte materials combining zirconia with ceria, alumina, and silica in specific proportions (e.g., 70-90 wt% zirconia, 5-20 wt% ceria, 1-10 wt% alumina, 1-10 wt% silica) to achieve both reliability and low power consumption at operating temperatures of 150°C or lower
2Duration of action of stationary object
If zirconia temperature is increased to hundreds of degrees C. for durability, then material durability is improved, but handling difficulty increases and power consumption reaches 100 W
Solution Approach 1:
The patent changes the operating temperature parameter to 150°C or lower, transforming the handling characteristics from difficult high-temperature operations to easily manageable low-temperature operations while maintaining durability through optimized material composition
3Reliability
If insulating film is added to prevent oxygen ion intake from edge face, then surface-conduction current is reduced, but device complexity increases
Solution Approach 1:
The patent introduces an insulating film as an intermediary layer between the solid electrolyte and the lower electrode, specifically at the edge face region, to prevent oxygen ion leakage and reduce surface conduction current while maintaining overall structural simplicity
Solution Approach 2:
The patent applies the insulating film locally at the edge face region where oxygen ion leakage occurs, rather than covering the entire sensor structure, thereby reducing surface conduction current with minimal increase in device complexity
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 solution effectively reduces surface-conduction current, achieving low power consumption and improved durability, making it suitable for accurate humidity measurement across various environments, including high-temperature and condensation conditions.
Implementation Method 1
a solid electrolyte layer disposed on the porous lower electrode in an opening formed by patterning the insulating film, and further disposed on the insulating film surrounding the opening
Implementation Method 2
the insulating film realizes non-contact between an edge face of the solid electrolyte layer and the porous lower electrode, in order to suppress the intake of oxygen (O) ion from the edge face
Data Source
AI summary
The limiting-current type gas sensor includes: a porous lower electrode disposed on a substrate; an insulating film disposed on the porous lower electrode; a solid electrolyte layer disposed on the porous lower electrode in an opening formed by patterning the insulating film, and further disposed on the insulating film surrounding the opening; and a porous upper electrode disposed on the solid electrolyte layer, wherein the insulating film realizes non-contact between an edge face of the solid electrolyte layer and the porous lower electrode, in order to suppress the intake of oxygen (O) ion from the edge face of the solid electrolyte layer, and thereby the surface-conduction current component between the porous upper electrode and the porous lower electrode can be reduced. There can be provided the limiting-current type gas sensor capable of reducing the surface-conduction current component and realizing low power consumption.