Stabilized Zirconia High-Temperature Sensor
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Solution Overview
Problem
High-temperature temperature sensors used in the automotive industry face challenges in withstanding extreme temperature gradients and rapid temperature changes without drifting or shifting measurement characteristics, especially when exposed to temperatures up to 1,100°C.
Innovation Solution
A high-temperature sensor with a substrate made of stabilized zirconium oxide or zirconium oxide ceramic, coated with an insulation layer and a ceramic intermediate layer, featuring sacrificial electrodes and a protective cover to stabilize the resistance structure and prevent thermal expansion-induced voltage, while also using a porous intermediate layer to match thermal expansion and protect against harmful ions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the temperature sensor uses a flat resistance structure to measure temperature, then the measurement can be taken close to the engine, but the sensor cannot withstand high temperatures and temperature gradients without drifting or destruction
Solution Approach 1:
A ceramic intermediate layer is introduced between the resistance structure and the zirconium oxide substrate. This intermediate layer acts as a mediator that protects the resistance structure from direct exposure to harmful ions in the high-temperature environment while matching thermal expansion properties, thereby enabling the sensor to withstand temperatures up to 1100°C without measurement drift or destruction
Solution Approach 2:
The sensor employs a composite structure combining zirconium oxide substrate, ceramic intermediate layer, insulation layer, and protective cover. This multi-layer composite material system provides both high-temperature resistance and measurement stability by distributing thermal and chemical stresses across different material layers with complementary properties
2Speed
If the temperature sensor is designed for fast reaction times, then the sensor responds quickly to temperature changes, but the sensor cannot withstand rapid temperature changes without drifting or shifting measurement characteristics
Solution Approach 1:
The ceramic intermediate layer has specifically optimized thermal and mechanical parameters including thermal conductivity, thermal expansion coefficient, and porosity. These parameter changes in the intermediate layer enable it to buffer rapid temperature changes, allowing the sensor to maintain measurement characteristic stability even during fast temperature transitions while preserving quick reaction times
3Temperature
If the zirconium oxide substrate is used without stabilization, then the substrate can operate at high temperatures, but thermal expansion causes voltage in the resistance structure leading to measurement drift
Solution Approach 1:
The zirconium oxide substrate is stabilized with oxides of trivalent and pentavalent metals to control its thermal expansion properties. This thermal expansion stabilization ensures that the substrate expands and contracts in a predictable manner at high temperatures, preventing unwanted voltage generation in the resistance structure and maintaining measurement accuracy throughout the operating temperature range
4Adaptability or versatility
If the resistance structure is exposed to harmful ions at high temperatures, then the sensor can operate in the exhaust environment, but the resistance structure becomes poisoned and drifts
Solution Approach 1:
The ceramic intermediate layer serves as a protective intermediary between the resistance structure and the harmful exhaust environment. It allows the sensor to operate in the harsh exhaust environment while preventing harmful ions from reaching and poisoning the resistance structure, thereby maintaining long-term reliability and resistance structure stability
Solution Approach 2:
Sacrificial electrodes are provided that can be consumed or degraded to protect the resistance structure. These sacrificial elements act as a disposable protective layer that absorbs harmful effects, allowing the main resistance structure to remain stable and functional for extended periods in the harsh exhaust environment
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 provides a stable and durable temperature sensor capable of withstanding up to 5,000 rapid temperature changes at 1,000°C without significant drift or destruction, maintaining accurate measurements and extending service life.
Implementation Method 1
By stabilizing the crystal structure with trivalent and pentavalent metal oxides, the thermal expansion of the substrate can be matched to the thermal expansion of the intermediate layer and the noble metals of the resistor structure. As a result, a thermally induced voltage in the resistance structure can be avoided or reduced.
Implementation Method 2
the ceramic intermediate layer being porous and at least two sides of the resistance structure being framed by at least two electrodes
Data Source
Figure 1
AI summary
The invention relates to temperature sensors, in particular high-temperature sensors, having an optionally coated substrate, at least one resistor structure, and at least two connection contacts. The connection contacts electrically contact the resistor structure, and the substrate is made of zirconium oxide or a zirconium oxide ceramic stabilized with oxides of a trivalent metal and a pentavalent metal. The substrate is coated with an insulation layer and the resistor structure and the free regions of the insulation layer, on which no resistor structure is disposed, are at least partially coated with a ceramic intermediate layer. A protective layer and/or a cover is disposed on the ceramic intermediate layer. At least one electrode may be disposed, at least at one connection contact, alongside the resistor structure on the substrate. The invention also relates an exhaust-gas system for controlling and/or regulating an engine, particularly a motor vehicle engine, containing these temperature sensors.