Thermistor Sintered Body Composition for Stable B Constant
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Solution Overview
Problem
In industrial production, thermistor sintered bodies often deviate from the aimed composition, leading to unstable B constants, which affects their ability to accurately detect temperature over a wide range.
Innovation Solution
A thermistor sintered body composed of a Y2O3 phase and a Y(Cr, Mn)O3 phase, with specific ratios of Cr, Mn, Ca, and Sr, along with a sea-island structure, stabilizes the B constant by dissolving Ca and Sr in the Y(Cr, Mn)O3 phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a thermistor sintered body is produced with a specific aimed composition, then the desired B constant can be obtained, but composition deviation occurs in industrial production leading to unstable B constant
Solution Approach 1:
The invention changes the compositional parameters by introducing Ca and Sr as additive elements in specific ranges (Ca: 1-8 mol%, Sr: 1-25 mol%). These parameter changes create a composition buffer zone that absorbs deviations, allowing the B constant to remain stable even when production variations occur. The patent specifies that Ca and Sr should be contained in the sintered body at these controlled levels to achieve parameter robustness.
Solution Approach 2:
The invention creates a composite material system by combining multiple elements (Cr, Mn, Ca, Sr, Y) in a Y(Cr, Mn)O3 phase with Y2O3 phase. This composite structure integrates the stabilizing effects of Ca and Sr with the functional Cr-Mn system, resulting in a material that maintains stable B constant characteristics despite compositional variations. The composite nature provides redundancy and stability against deviation.
2Measurement precision
If the B constant is made small to enable wide temperature range detection, then temperature detection accuracy improves, but the thermistor becomes more sensitive to composition variations
Solution Approach 1:
The invention applies beforehand cushioning by pre-introducing Ca and Sr elements into the composition before production variations occur. These elements act as a cushion or buffer that absorbs the impact of composition deviations, protecting the B constant from fluctuation. This prior cushioning allows the thermistor to maintain both small B constant and composition insensitivity simultaneously.
Solution Approach 2:
Ca and Sr function as intermediary elements that mediate between the Cr-Mn functional system and the Y2O3 matrix. These intermediary elements stabilize the overall system, allowing the Cr-Mn portion to provide the desired small B constant while the Ca-Sr portion provides compositional buffering, thus resolving the conflict between measurement precision and manufacturing precision.
3Adaptability or versatility
If Ca and Sr are added to stabilize the B constant, then the composition range for stable B constant widens, but the number of elements to control increases
Solution Approach 1:
The invention applies universality by making Ca and Sr serve multiple functions simultaneously: they act as stabilizers for the B constant, expand the safe composition range, and provide buffering against production variations. This multi-functionality means that adding these elements increases adaptability without proportionally increasing complexity, as they fulfill several roles with a single compositional adjustment.
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 combined addition of Ca and Sr ensures a stable B constant across a wide composition range, enabling accurate temperature detection from -50°C to approximately 1200°C, suitable for automotive exhaust-gas treatment devices and high-temperature measurements.
Implementation Method 1
Ca and Sr are preferably dissolved in the Y(Cr, Mn)O3 phase
Implementation Method 2
a temperature sensor has been widely used that uses a thermistor of which the electric resistance value (hereinafter simply referred to as resistance value) changes according to a temperature
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3B
AI summary
The purpose of the present invention is to provide a thermistor sintered body for which a desired B constant can be stably obtained even if a composition deviation occurs in an additive element. The thermistor sintered body of the present invention comprises a sintered body that comprises a Y2O3 phase and a Y(Cr),Mn)O3 phase, and a chemical composition of Cr, Mn, Ca, and Y excluding oxygen is Cr: 3 to 12 mol%, Mn: 5 to 15 mol%, Ca: 1 to 8 mol%, and Sr: 1 to 25 mol%, with the remainder comprising inevitable impurities and Y. With the thermistor sintered body of the present invention, Ca and Sr can also be dissolved in a Y(Cr,Mn)O3 phase.