Limiting-Current Gas Sensor with Porous Transition Metal Oxide Passages
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Solution Overview
Problem
Existing limiting-current type gas sensors exhibit significant variation in temperature coefficients of limiting current values, making it difficult to accurately and stably measure oxygen concentration in target gases.
Innovation Solution
A limiting-current type gas sensor design incorporating a solid electrolyte, a first porous metal electrode, and gas feed and discharge passages formed from porous transition metal oxides (Ta2O5, TiO2, or Cr2O3) with higher melting points than the electrodes, which helps in uniform distribution of vacancies and reduced thermal strain, thereby stabilizing the limiting current value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional limiting-current type oxygen sensor is used with platinum or palladium electrodes and thin solid electrolyte film, then the sensor structure is simple and manufacturing is easy, but the temperature coefficient of limiting current value varies significantly among sensors, making accurate and stable oxygen concentration measurement difficult
Solution Approach 1:
The gas feed passage is formed as a porous structure made of transition metal oxide, which allows controlled gas transport to the first electrode while maintaining structural stability at operating temperatures. The porous nature enables uniform gas distribution and reduces temperature-induced variations in limiting current characteristics.
Solution Approach 2:
The invention changes the material parameter of the gas feed passage from conventional metals to transition metal oxides with higher melting points. This parameter change stabilizes the thermal and structural properties of the sensor, reducing the variation in temperature coefficients among individual sensors and improving measurement reliability.
2Reliability
If the gas feed passage is formed of material with lower melting point than the electrode, then manufacturing process is simpler, but thermal strain occurs during operation, causing variation in temperature coefficient and response time
Solution Approach 1:
The invention specifies that the gas feed passage material must have a higher melting point than the electrode material. This parameter constraint prevents thermal strain during operation, as the gas feed passage maintains structural integrity at operating temperatures. The transition metal oxide materials (Ta2O5, TiO2, Cr2O3) satisfy this requirement while providing stable thermal and mechanical 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 design reduces variations in temperature coefficients and response times, enhancing the accuracy and stability of oxygen concentration measurements in gas sensors.
Implementation Method 1
The gas feed passage is formed of a porous transition metal oxide. The porous structure enables uniform gas distribution through capillary forces, reducing thermal strain and stabilizing the limiting current value
Implementation Method 2
The oxygen ions are conducted through the thin solid electrolyte film and moved to the second electrode
Data Source
AI summary
Disclosed herein is a limiting-current type gas sensor including a solid electrolyte, a first electrode disposed on the solid electrolyte, a second electrode disposed on the solid electrolyte, and a gas feed passage extending between a gas inlet and a first portion of the first electrode, the first portion facing the solid electrolyte. The first electrode is a first porous metal electrode. The gas feed passage is formed of a first porous transition metal oxide having a second melting point higher than a first melting point of the first electrode. The first porous transition metal oxide is Ta2O5, TiO2, or Cr2O3.