Thermistor Element High-Temperature Stability
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Solution Overview
Problem
Conventional thermistor elements face reliability issues when detecting high temperatures above 900°C, as they tend to have low reliability and significant changes in resistance values under such conditions.
Innovation Solution
A thermistor element with a thermistor layer composed of oxides expressed by the formula YaCabCrcAldM1eO3, where 'a' ranges from 0.5 to 0.99, 'b' from 0.01 to 0.50, 'c' from 0.06 to 0.64, 'd' from 0.01 to 0.94, and 'e' from 0.00 to 0.35, and 'M1' is selected from Co, Sn, Nd, Pr, or Ni, without Sr and Mn, integrated with internal Pt electrode layers and an insulating layer, ensuring minimal resistance change at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional sintered conductive oxide (containing Sr and Mn) is used for thermistor layer, then manufacturing is easier and cost is lower, but reliability at high temperature over 900°C deteriorates with significant resistance value changes
Solution Approach 1:
The invention changes the compositional parameters of the thermistor layer by specifying precise ranges for a, b, c, d, and e in the formula YaCabCrcAldM1eO3, and by selecting specific M1 elements (Co, Sn, Nd, Pr, Ga, or Ni) while excluding Sr and Mn. These parameter changes enable the thermistor to maintain stability at temperatures over 900°C, resolving the reliability issue without complicating the manufacturing process
Solution Approach 2:
The invention uses a composite oxide material comprising multiple elements (Y, Ca, Cr, Al, and M1) in specific proportions. This composite material structure provides both the desired high-temperature stability and manufacturability, as the components can be mixed and sintered using conventional processes while achieving superior performance
2Measurement precision
If conventional thermistor materials are used, then device structure is simpler, but measurement precision deteriorates due to significant resistance value changes at high temperature
Solution Approach 1:
By precisely controlling the compositional parameters (a, b, c, d, e ranges and M1 selection) of the thermistor layer, the invention achieves minimal resistance value changes at high temperatures. This enables accurate temperature measurement over 900°C without requiring complex compensation circuits or additional sensors, thus maintaining measurement precision without increasing device complexity
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 highly reliable thermistor element with minimal resistance change even at high temperatures, maintaining stability and accuracy, and preventing delamination due to its multilayer structure and close linear expansion coefficients between materials.
Implementation Method 1
a thermistor layer comprising oxide expressed by a composition formula YaCabCrcAldM1eO3
Data Source
AI summary
A highly-reliable thermistor element even when used at a relatively high temperature comprising; element body incorporating two or more internal electrode layers arranging thermistor layer in-between, a pair of terminal electrodes each connected to the mutually faced internal electrode layers and formed on exterior surface of the element body, and lead terminal connected to the terminal electrode, characterized in that the thermistor layer comprises oxide expressed by a composition formula YaCabCrcAldM1eO3 and the thermistor layer substantially does not include Sr or Mn.