Partially Stabilized Zirconia Solid Electrolyte for Thermal Cycle Strength
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Solution Overview
Problem
Conventional solid electrolytes made of partially stabilized zirconia lack sufficient strength against cooling and heating cycles due to unstable monoclinic phase transformations at crystal grain boundaries, leading to internal stress and potential damage.
Innovation Solution
A solid electrolyte comprising partially stabilized zirconia with mixed phase particles containing 15 volume percent or more of low-concentration phases, where the mixed phase particles have an average size of 0.3 to 1.5 μm and a presence rate of 90 volume percent or more, absorbing volume changes and mitigating internal stress through a high-concentration phase within the same crystal particle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional partially stabilized zirconia is used as solid electrolyte, then the gas sensor can detect oxygen concentration, but the sensor lacks sufficient strength against cooling and heating cycles due to internal stress from phase transformations at crystal grain boundaries
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the center region contains mixed phases (monoclinic and cubic) to absorb volume changes, while the outer region maintains high cubic phase content for stability. This localized phase distribution resolves the contradiction by concentrating the stress-absorbing function in specific regions rather than uniformly distributing phases throughout the material.
Solution Approach 2:
The patent uses composite materials by combining zirconia with stabilizers (yttria, calcia, magnesia, or scandia) to create partially stabilized zirconia with controlled phase compositions. The composite structure includes both monoclinic and cubic phases in specific ratios, allowing the material to simultaneously achieve structural integrity and stress tolerance during thermal cycling.
2Temperature
If the solid electrolyte is exposed to high temperatures exceeding 1,000°C, then the gas sensor operates in high-temperature environments, but internal damage occurs due to phase transformations
Solution Approach 1:
The patent implements beforehand cushioning by pre-forming the core-shell phase structure before high-temperature exposure. The central region's mixed phase composition is designed in advance to accommodate and cushion the volume changes that occur during thermal cycling, preventing internal damage before it can occur during high-temperature operation.
Solution Approach 2:
The patent exploits phase transitions by deliberately incorporating monoclinic phase regions in the core that can transform during thermal cycling. These controlled phase transitions in the central region absorb the stress of temperature changes, while the outer cubic-rich region maintains structural integrity, enabling high-temperature operation without internal damage.
3Strength
If uniform phase distribution is used in the solid electrolyte, then the manufacturing process is simplified, but the strength against thermal cycles is insufficient due to lack of stress absorption mechanisms
Solution Approach 1:
The patent applies segmentation by dividing the solid electrolyte into distinct regions: a central region with mixed phases for stress absorption and an outer region with high cubic phase content for stability. This spatial segmentation of phase distributions allows each region to perform its specific function, resolving the contradiction between strength and manufacturing 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 solid electrolyte exhibits excellent strength against cooling and heating cycles, maintaining reliability even at high temperatures exceeding 1,000°C, reducing the likelihood of internal damage and enhancing the durability of gas sensors.
Implementation Method 1
internal stress generated by phase transformations at crystal grain boundaries
Implementation Method 2
the high-concentration phase absorbs volume changes, mitigating internal stress
Implementation Method 3
a production method involving heat treatment, mixing, shaping, and firing to achieve these phase distributions
Implementation Method 4
a production method involving heat treatment, mixing, shaping, and firing to achieve these phase distributions
Data Source
AI summary
The invention relates to a solid electrolyte including partially stabilized zirconia, a producing method thereof, and a gas sensor including a solid electrolyte. The partially stabilized zirconia includes crystal particles, the crystal particles include mixed phase particles each having a high-concentration phase and a low-concentration phase, the high-concentration phase being defined such that a concentration of the stabilizer is 4.7 mol % or more, the low-concentration phase being defined as a concentration of the stabilizer is less than 4.7 mol %.