Conductive Sintered Oxide Thermistor for Wide-Temperature Measurement
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Solution Overview
Problem
Thermistor elements used in temperature measurements, particularly in exhaust gas temperature applications, face challenges in achieving accurate measurements over a wide temperature range (-40°C to +600°C) and detecting failures such as wire breakage and short-circuiting, due to limitations in the temperature coefficient of resistance (constant B) and stability at high temperatures.
Innovation Solution
A conductive sintered oxide with a first crystal phase of RE1 4 Al 2 O 9 and a second crystal phase with a perovskite structure, where RE1 includes Yb and/or Lu, and the second crystal phase excludes Cr, allowing for a reduced value of constant B, enabling stable temperature measurements across a wide range and precise failure detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional conductive sintered oxide with constant B of 2000-3000K is used, then temperature measurement is possible, but the measurement range is limited and cannot cover -40°C to +600°C effectively
Solution Approach 1:
The patent changes the chemical composition parameters of the sintered oxide by incorporating specific rare earth elements (Yb, Lu) and controlling the content of Cr and other metal elements. This composition optimization reduces the constant B value to 2000K or less, enabling accurate temperature measurements across the extended range of -40°C to +600°C
Solution Approach 2:
The patent creates a composite sintered oxide material combining multiple rare earth elements (Yb, Lu) with controlled amounts of Cr and other metal elements. This composite structure achieves the desired electrical properties and temperature characteristics that cannot be obtained with single-element oxides, facilitating wide-range temperature measurement
2Reliability
If Cr is included in the sintered oxide to achieve desired electrical properties, then conductivity is improved, but chromium volatilization at high temperatures causes property variations and instability
Solution Approach 1:
The patent optimizes the Cr content parameter within specific ranges (0.1-5.0 wt%) and introduces Yb and Lu elements to compensate for Cr volatilization. This parameter control prevents excessive chromium loss while maintaining electrical properties and achieving high-temperature stability
Solution Approach 2:
The patent extracts the harmful effect of chromium volatilization by limiting Cr content and replacing excessive Cr with Yb and Lu elements that have lower volatility. This separation of functions allows the material to maintain conductivity without suffering from chromium loss at high temperatures
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 conductive sintered oxide provides a thermistor element with a constant B of 2,000K or less, enabling suitable temperature measurements and precise failure detection over -40°C to +600°C, while maintaining stability and reducing property variations due to chromium volatilization.
Implementation Method 1
a conductive sintered oxide which has electrically conductive properties and which changes in resistance with a change in temperature
Data Source
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AI summary
A conductive sintered oxide including: a first crystal phase represented by REl4Al2O9 and a second crystal phase having a perovskite structure represented by (RE21-cSLc)(AlxM1y)O3. RE1 is a first element group consisting of Yb and/or Lu and at least one element selected from Group IIIA elements excluding Yb, Lu and La. RE2 is a second element group consisting of at least one element selected from Group IIIA elements excluding La and including at least one of the elements constituting the first element group RE1. SL is an element group consisting of at least one of Sr, Ca and Mg and which includes Sr as a main element, and M1 is an element group consisting of at least one element selected from Groups IVA, VA, VIA, VIIA and VIII excluding Cr. The coefficient c is in the range of 0.18<c<0.50, and the coefficients x and y are in the range of 0.95≤x+y≤1.1.