Partially Stabilized Zirconia Solid Electrolyte Thermal Stability
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Solution Overview
Problem
Conventional solid electrolytes made of partially stabilized zirconia face issues with thermal stability and reliability due to differences in coefficient of thermal expansion with dissimilar material members, leading to peeling and cracking, especially in high-temperature environments exceeding 1,000°C, which is a challenge for gas sensors used in internal combustion engines.
Innovation Solution
A solid electrolyte composed of partially stabilized zirconia with stabilizer low-concentration and high-concentration phase particles, where the abundance ratio of high-concentration phase particles is greater than 70% and adjacent low-concentration phase particles with average sizes over 0.1 μm are present, reducing thermal stress and matching the coefficient of thermal expansion with dissimilar materials like alumina or spinel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional partially stabilized zirconia is used as solid electrolyte, then oxygen concentration detection function is achieved, but thermal stability deteriorates due to coefficient of thermal expansion mismatch with dissimilar materials
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of stabilizer concentration within the zirconia particles. Specifically, the particle centers have lower stabilizer concentration (0-3 mol%) while the periphery has higher stabilizer concentration (6-8 mol%), resulting in different crystal phases (monoclinic at center, cubic at periphery) that collectively match the thermal expansion coefficient of dissimilar materials like alumina or spinel, thereby preventing peeling and cracking during thermal cycling.
Solution Approach 2:
The patent employs composite materials by combining different crystal phases (monoclinic and cubic zirconia) within the same particle structure. This composite phase structure allows the solid electrolyte to achieve both the required ionic conductivity and the matched coefficient of thermal expansion with dissimilar materials, resolving the thermal stability issue without sacrificing sensor functionality.
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 proposed solid electrolyte configuration enhances thermal stability, preventing damage and peeling/cracking during cooling/heating cycles, ensuring high reliability and durability even at extreme temperatures, thus improving the performance and lifespan of gas sensors.
Implementation Method 1
partially stabilized zirconia in which a stabilizer forms a solid solution in zirconia
Implementation Method 2
matching the coefficient of thermal expansion with dissimilar materials like alumina or spinel, reducing thermal stress
Data Source
AI summary
A solid electrolyte includes partially stabilized zirconia in which a stabilizer forms a solid solution in zirconia. The partially stabilized zirconia includes, as crystal particles that configure the partially stabilized zirconia, stabilizer low-concentration phase particles of which concentration of the stabilizer at a particle center is less than 4.7 mol % and stabilizer high-concentration phase particles of which the concentration of the stabilizer at the particle center is equal to or greater than 4.7 mol %. The partially stabilized zirconia includes an adjacent particle portion in which two or more particles of the stabilizer low-concentration phase particles of which an average particle size is greater than 0.1 μm are adjacent. An abundance ratio of the stabilizer high-concentration phase particles on a cross-section of the solid electrolyte is equal to or greater than 70% in terms of area ratio relative to all crystal particles.