Nitrogen-oxide Gas Sensor Using P-type and N-type Metal Oxide Films
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing nitrogen-oxide gas sensors face challenges in accurately measuring nitric oxide and nitrogen dioxide concentrations simultaneously, especially at high temperatures, due to limitations in measurement methods such as low melting points of sensing electrodes, temperature-dependent current measurements, and decreased accuracy when measuring mixtures of nitrogen dioxide and nitric oxide.
Innovation Solution
A nitrogen-oxide gas sensor design incorporating an oxide ion conductive solid electrolyte, p-type semiconductor metal oxide films, and n-type semiconductor metal oxide layers, with a power source and measurement unit to measure electric potential differences, ensuring stability and accuracy by using p-type and n-type semiconductor metal oxides in a stack configuration or as buffer layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a solid-state nitrate sensing electrode is used in a solid electrolyte to measure nitrogen-oxide concentration via equilibrium potential, then measurement capability is achieved, but the sensor cannot operate at high temperatures due to low melting point of the sensing electrode
Solution Approach 1:
The patent changes the material parameters of the sensing electrode from low-melting solid-state nitrate to high-melting metal oxide (such as tungsten oxide, molybdenum oxide, or their alloys), enabling operation at high temperatures (600-1000°C) while maintaining sensor stability and reliability
Solution Approach 2:
The patent uses composite material structures including metal oxide sensing electrodes combined with solid electrolytes (such as YSZ - yttria-stabilized zirconia), creating a composite system that achieves both high-temperature stability and nitrogen-oxide sensing capability
2Measurement precision
If a current type sensor with oxygen pumping cell is used to measure nitrogen-oxide, then measurement capability is achieved, but structural complexity increases and measurement accuracy decreases at low concentrations (few hundreds ppm or below)
Solution Approach 1:
The patent removes the complex oxygen pumping cell structure from the sensor design, simplifying the overall device while maintaining measurement capability through direct metal oxide sensing electrode reactions with nitrogen-oxide
Solution Approach 2:
The patent changes the measurement principle from current measurement via oxygen ion decomposition to potential difference measurement via metal oxide sensing electrode reactions, enabling accurate detection of low concentrations (few hundreds ppm or below) without requiring complex pumping structures
3Measurement precision
If mixed dislocation method with metal oxide sensing electrode and noble metal reference electrode is used, then measurement capability is achieved, but measurement accuracy decreases due to different electromotive forces from decomposition of nitrogen dioxide and nitric oxide
Solution Approach 1:
The patent applies different material properties to different regions: the sensing electrode uses metal oxide with specific reactivity to nitrogen-oxide, while the reference electrode uses noble metal with stable, consistent reactivity, creating localized functional zones that compensate for the different electromotive forces of nitrogen dioxide and nitric oxide decomposition
Solution Approach 2:
The patent changes the reference electrode material to noble metal (such as platinum or gold) with stable electrochemical properties, and adjusts the sensing electrode material composition (metal oxides like tungsten oxide, molybdenum oxide, or their alloys) to achieve consistent potential responses for both nitrogen dioxide and nitric oxide, thereby improving measurement accuracy for mixed gases
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 design allows for simultaneous measurement of nitric oxide and nitrogen dioxide with increased accuracy and long-term stability, even at high temperatures, by optimizing the reaction rates and voltage stability through the use of p-type and n-type semiconductor metal oxides.
Implementation Method 1
an oxide ion conductive solid electrolyte
Implementation Method 2
a first film that contacts the solid electrolyte and is made of a p-type semiconductor metal oxide; a second film that contacts the solid electrolyte and is made of a p-type semiconductor metal oxide; an n-type semiconductor metal oxide that is included in at least one of the first and second films
Data Source
AI summary
The present invention provides a nitrogen-oxide gas sensor that is able to measure nitric oxide and nitrogen dioxide at the same time and ensure measurement accuracy and long stability. For these purposes, the nitrogen-oxide gas sensor includes: an oxide ion conductive solid electrolyte; a primary film that contacts the solid electrolyte and is made of a p-type semi-conductor metal oxide; a secondary film that contacts the solid electrolyte and is made of a p-type semiconductor metal oxide; an n-type semiconductor metal oxide that is included in at least one of the primary and secondary films; a power source that applies electric power to the primary and secondary films by electrically connecting a primary node to the primary film and a secondary node to the secondary film; and a measurement unit that measures the electric potential difference between the primary and secondary nodes.