Electrochemical Gas Sensor Thin Film Electrolyte Annealing
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Solution Overview
Problem
Conventional electrochemical gas sensors using solid state ion-conducting electrolytes face challenges such as high operation temperatures, instability in humidity, complex stoichiometry, and incompatibility with thermal expansion and deposition processes, limiting design flexibility and sensor performance.
Innovation Solution
A method for manufacturing an electrochemical gas sensor using a non-ion-conducting thin film of ceramic or glass, deposited by CVD, ALD, or PVD, which is converted into an ion-conducting electrolyte through annealing, allowing for lower operating temperatures and improved compatibility with established deposition processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sintered solid state ion conductor with thickness of several 100 μm is used as electrolyte, then sufficient ionic conductivity is achieved, but high operation temperature (500°C or more) and high processing temperature (1100°C or more) are required
Solution Approach 1:
The patent replaces thick sintered solid state ion conductors (several 100 μm) with thin films of ion-conducting materials (e.g., lithium phosphate, lithium silicate) deposited by CVD, ALD, or PVD. These thin films achieve sufficient ionic conductivity at much lower operating temperatures (below 500°C) due to their reduced thickness and optimized composition, eliminating the need for high-temperature operation while maintaining reliable ion transport.
Solution Approach 2:
The patent changes key parameters of the electrolyte material including composition (using lithium-containing compounds like lithium phosphate or lithium silicate), thickness (reducing from 100 μm to thin film scale), and deposition method (CVD, ALD, PVD). These parameter changes enable the electrolyte to function at lower temperatures while maintaining ionic conductivity, directly resolving the contradiction between reliability and operating temperature.
2Reliability
If complex stoichiometry solid electrolytes are used, then ion conductivity is achieved, but compatibility with established chemical and physical deposition processes becomes difficult
Solution Approach 1:
The patent simplifies the stoichiometry of the electrolyte material by using well-known compounds like lithium phosphate (Li3PO4) or lithium silicate (Li2SiO3) with straightforward compositions. These materials can be deposited using established CVD, ALD, or PVD processes without requiring complex stoichiometric control, thereby improving ease of manufacture while maintaining ion conductivity through optimized thin film design and post-deposition thermal treatment.
Solution Approach 2:
The patent employs materials and processes that are readily available and well-understood in semiconductor manufacturing. By using conventional deposition techniques with simple stoichiometry, the manufacturing process becomes more accessible and less costly, trading away the need for complex material synthesis in favor of established industrial processes that can reliably produce ion-conducting thin films.
3Reliability
If lithium or sodium ions are used as mobile ions in solid electrolyte, then high ion mobility is achieved, but stoichiometry complexity increases and thermal expansion compatibility decreases
Solution Approach 1:
The patent uses lithium or sodium ions as mobile ions in thin film electrolytes with simplified stoichiometry (e.g., lithium phosphate Li3PO4, lithium silicate Li2SiO3). The thin film geometry and controlled deposition parameters compensate for potential stoichiometry challenges, while the high ion mobility of lithium/sodium enables efficient ion transport. Thermal expansion compatibility is improved by designing multi-layer structures with appropriate buffer layers and optimizing film composition to match the thermal properties of adjacent sensor components.
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 approach simplifies the manufacturing process, reduces operating temperatures, and enhances sensor performance by enabling more flexible material choices and compatibility with MEMS technology, while maintaining high sensitivity and stability.
Implementation Method 1
the thin film is converted into an ion-conducting electrolyte through annealing
Implementation Method 2
deposited by CVD, ALD, or PVD
Implementation Method 3
deposited by CVD, ALD, or PVD
Data Source
Figure 1A~2
Figure 3A~4
Figure 5
AI summary
In a method for manufacturing an electrochemical gas sensor for sensing a target gas, a semi-manufactured gas sensor is provided. The semi-manufactured gas sensor comprises a substrate (5) supporting an arrangement comprising a thin film (2) of a thickness s ≤ 5µm arranged between a sensing electrode (1) configured to chemically interact with the target gas and a reference electrode (3) facing the substrate (5). The thin film (2) is an electronically non-conducting and ionically non-conducting ceramic or glass. The arrangement then is heated to an annealing temperature (T1) for irreversibly turning the thin film (2) into an ionic conductor by incorporating mobile ions released from the sensing electrode (1) in response to the heating.