Layered Oxygen Sensor Element for Low-Power Heat Insulation
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Solution Overview
Problem
Existing oxygen sensors using ceramic sintered bodies face issues with mechanical strength, durability, and mass productivity due to the fusion of wire materials at hot spots, which affects sensor sensitivity and power consumption, and the use of conventional heat insulating materials leads to separation and degradation of sensor characteristics.
Innovation Solution
A ceramic oxygen sensor element with a layered structure, where a sensing layer is sandwiched between heat insulating layers made of Ln2BaCuO5 with added LnBa2Cu3O7−δ, allowing simultaneous baking and improving heat insulation properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a wire material is constricted and thinned to generate a hot spot for reducing power consumption, then power consumption is reduced, but the wire material is more likely to be fused and mechanical strength decreases
Solution Approach 1:
A heat insulating layer made of Ln2BaCuO5 is introduced as an intermediary between the hot spot region and the surrounding environment. This layer prevents excessive heat accumulation that would cause wire fusion while maintaining the hot spot's heating function, thus reducing power consumption without compromising durability
Solution Approach 2:
The wire material is constricted to change its geometric parameters (reduced cross-sectional area) at a specific position, which increases resistance and generates a hot spot. This parameter change enables localized heating to reduce overall power consumption while the heat insulating layer prevents excessive temperature rise
2Temperature
If conventional heat insulating materials (alumina, magnesia, yttria, barium titanate) are used to cover the hot spot, then heat insulation is improved, but these materials react with LnBa2Cu3O7−δ during baking, degrading sensor sensitivity
Solution Approach 1:
The heat insulating layer is made of Ln2BaCuO5, which has compositional homogeneity with the sensor element material LnBa2Cu3O7−δ (both are rare earth-based cuprates). This compositional similarity prevents chemical reactions during baking, maintaining sensor sensitivity while providing effective heat insulation
Solution Approach 2:
The invention uses a composite structure where Ln2BaCuO5 heat insulating layer is combined with LnBa2Cu3O7−δ sensor element material. This composite material system ensures compatibility during sintering while achieving both heat insulation and sensitivity preservation
3Temperature
If conventional heat insulating materials are used, then heat insulation is achieved, but they show different sintering behaviors from LnBa2Cu3O7−δ, causing separation at the interface and degrading mass productivity
Solution Approach 1:
Both the heat insulating layer (Ln2BaCuO5) and sensor element material (LnBa2Cu3O7−δ) are rare earth-based cuprates with similar crystal structures and sintering characteristics. This material homogeneity ensures they undergo sintering at comparable temperatures and rates, preventing interface separation and enabling simultaneous baking for high mass productivity
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 layered structure ensures simultaneous sintering without layer separation, enhances mechanical strength, maintains sensor sensitivity, and achieves electric power saving by reducing heat dissipation, thereby improving mass productivity and portability.
Implementation Method 1
Heat insulating layers represented as a composition formula Ln2BaCuO5 (Ln denotes rare earth element) are arranged so as to cover a predetermined portion on an outer surface of the ceramic sintered body
Implementation Method 2
utilizes a hot spot phenomenon that a part of a wire material configuring the sensor is red-heated by applying a voltage
Implementation Method 3
utilizes a hot spot phenomenon that a part of a wire material configuring the sensor is red-heated by applying a voltage
Data Source
AI summary
An oxygen sensor element that can achieve electric power saving without losing sensor characteristics has a structure in which an outer surface of a ceramic sintered body as a sensing layer made of a composition LnBa2Cu3O7−δ (Ln denotes rare earth element) is covered with heat insulating layers. A heat insulating material having a composition Ln2BaCuO5 is used for the heat insulating layers, and that composition Ln2BaCuO5 is added with 20 mol % of LnBa2Cu3O7−δ. This allows a sintering behavior of the heat insulating layers to come close to a sintering behavior of the sensing layer, and can thus prevent the occurrence of separation of the layers and cracks. The oxygen sensor element has a sandwich structure where the sensing layer is sandwiched between the heat insulating layers, thereby reducing the amount of heat dissipated from the sensing layer, and making it possible to achieve electric power saving.