Pt-Sr Conductive Material for High-Temperature Sensor Reliability
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Solution Overview
Problem
Conductive materials used in gas sensors and thermistors face challenges in maintaining mechanical strength and resistance stability at high temperatures, with Pt and Pt-Rh alloys being inadequate due to low mechanical strength, crystal grain coarsening, and high costs of Rh, limiting their application in fine wire formation and resistance change detection.
Innovation Solution
A conductive material comprising Pt with 400 to 10,000 ppm of Sr, where an intermetallic compound phase of Pt and Sr is dispersed, enhancing mechanical strength, workability, and resistance stability, while suppressing crystal grain coarsening and oxidation, allowing for the formation of fine wires with improved ductility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Pt is used as conductive material, then corrosion resistance and resistance stability are improved, but mechanical strength is insufficient and crystal grains coarsen at high temperatures
Solution Approach 1:
The invention uses a composite material system consisting of Pt matrix with SrO dispersoid particles. This composite structure combines the excellent corrosion resistance and electrical conductivity of Pt with the high melting point and fine grain refining effect of SrO, achieving both reliable corrosion resistance and enhanced mechanical strength at high temperatures.
Solution Approach 2:
The invention introduces SrO dispersoids at specific locations within the Pt matrix to create local reinforcement zones. These dispersoid particles are distributed throughout the material to pin grain boundaries and prevent coarsening, providing localized strengthening without compromising the overall corrosion resistance of the Pt matrix.
2Strength
If Rh is added to Pt to enhance mechanical strength, then strength is improved, but composition changes due to vapor pressure difference causing resistance variation
Solution Approach 1:
The invention replaces expensive Rh with SrO dispersoids that are more cost-effective. While Rh provides temporary strength enhancement, it suffers from vapor pressure differences causing composition drift. SrO particles are thermally stable and do not evaporate significantly, providing long-term compositional stability and resistance consistency.
Solution Approach 2:
The invention changes the strengthening mechanism from solid solution strengthening (Rh in Pt) to particle reinforcement (SrO dispersoids). This parameter change in the strengthening approach eliminates the vapor pressure mismatch issue while maintaining mechanical strength enhancement through a different physical mechanism.
3Strength
If oxide dispersed material is used to enhance strength, then mechanical strength is improved, but ductility decreases and fine wire formation becomes difficult
Solution Approach 1:
The invention optimizes the size parameter of SrO dispersoids to be extremely fine (0.1-10 μm) and controls their distribution density. This parameter optimization allows the material to maintain adequate ductility for wire drawing while still achieving strength enhancement. The fine size prevents excessive brittleness that would occur with larger oxide particles.
Solution Approach 2:
The SrO dispersoids are distributed uniformly throughout the Pt matrix rather than concentrated in specific regions. This uniform local distribution ensures that the material maintains consistent mechanical properties throughout, allowing for uniform deformation during wire drawing while still providing overall strength enhancement.
4Ease of operation
If fine wire with diameter of 50 μm or less is formed, then workability is improved, but mechanical strength becomes insufficient
Solution Approach 1:
The invention introduces SrO dispersoid particles that act as internal reinforcement segments within the fine wire structure. These particles divide and distribute stress throughout the wire cross-section, preventing stress concentration that would lead to failure. This segmentation effect allows fine wires to maintain adequate strength despite their small diameter.
Solution Approach 2:
The fine wire is formed as a composite material with Pt matrix and SrO dispersoids. This composite structure provides strength enhancement at the fine wire scale, where the surface-to-volume ratio is high and conventional strengthening mechanisms are less effective. The SrO particles provide nucleation sites and stress distribution that maintain strength in ultra-fine dimensions.
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 material achieves high mechanical strength, stable resistance ratio, and excellent corrosion and oxidation resistance, enabling the formation of fine wires with enhanced tensile strength and resistance stability even at high temperatures, suitable for applications in sensors and thermistors.
Implementation Method 1
an intermetallic compound phase formed of Pt and Sr is dispersed and precipitated in Pt
Implementation Method 2
The conductive material of the present invention has oxidation resistance and corrosion resistance, and the surface thereof is not to be covered with an oxide film even when exposed to a high temperature of 1,500° C. or higher
Implementation Method 3
a conductive material comprising: Pt; 400 to 10,000 ppm of Sr contained therein; and an inevitable impurity as the balance
Data Source
AI summary
Provided is a conductive material to be used for a resistor and a sensor, which is enhanced its mechanical strength while maintaining a stable resistance ratio. In the conductive material used for the resistor and the sensor, 400 to 10,000 ppm of Sr is contained in Pt, and the balance is an inevitable impurity. An intermetallic compound phase formed of Pt and Sr is precipitated and dispersed in Pt.