Partially Stabilized Zirconia Solid Electrolyte for Gas Sensors

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Solution Overview

Problem

Conventional solid electrolytes used in gas sensors experience thermal expansion hysteresis and damage due to differences in thermal expansion coefficients with dissimilar material members, leading to peeling and cracking, especially at high temperatures exceeding 1000°C, which affects their reliability and stability.

Innovation Solution

A solid electrolyte composed of partially stabilized zirconia with a stabilizer forming a solid solution, containing monoclinic and cubic phase particles, and stabilizer low-concentration phase particles with specific particle size distribution, reducing thermal expansion hysteresis and enhancing strength, is developed. This electrolyte is manufactured through a process involving mixing, molding, and sintering of zirconia raw materials with varying particle sizes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If conventional solid electrolytes are used in gas sensors, then the sensor can operate at high temperatures, but thermal expansion hysteresis and damage occur due to differences in thermal expansion coefficients with dissimilar material members, leading to peeling and cracking

Engineering Contradiction:

Improveoperating temperatureVSAvoidthermal expansion stability

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The patent changes the particle size distribution parameter of zirconia to resolve the thermal expansion contradiction. Specifically, it uses a bimodal distribution with 30-70 wt% of particles having 0.3-1.0 μm diameter and 70-30 wt% of particles having 1.0-3.0 μm diameter. This parameter change modifies the thermal expansion behavior to reduce hysteresis and improve reliability at high operating temperatures

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite microstructure within the solid electrolyte by combining zirconia particles of two different size ranges in specific proportions. This composite approach allows the material to exhibit optimized thermal expansion properties that reduce hysteresis while maintaining high-temperature operational capability

Inventive Principle:

Principle #40Composite materials

2Strength

If the zirconia particle size is reduced to improve strength, then the solid electrolyte becomes stronger, but the manufacturing precision and control of particle size distribution become more difficult

Engineering Contradiction:

Improvesolid electrolyte strengthVSAvoidparticle size control

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The patent segments the zirconia particle population into two distinct size groups (0.3-1.0 μm and 1.0-3.0 μm) with defined weight ratios. This segmentation strategy allows each size range to be controlled within feasible manufacturing tolerances while achieving the desired overall strength improvement through the optimized distribution

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent specifies precise particle size diameter ranges (0.3-1.0 μm and 1.0-3.0 μm) and their weight percentage distribution (30-70 wt% and 70-30 wt%). These parameter changes define a manufacturable particle size distribution that balances strength improvement with manufacturing controllability

Inventive Principle:

Principle #35Parameter changes

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 solid electrolyte with reduced thermal expansion hysteresis and increased strength, enabling reliable operation at high temperatures without internal damage, thus improving the stability and performance of gas sensors.

Implementation Method 1

partially stabilized zirconia in which a stabilizer forms a solid solution in zirconia

Methodology Applied

Scientific EffectSolid solution formation: Solid Solution Strengthening

Implementation Method 2

differences in thermal expansion coefficients with dissimilar material members, leading to peeling and cracking, especially at high temperatures exceeding 1000°C

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 3

This electrolyte is manufactured through a process involving mixing, molding, and sintering of zirconia raw materials with varying particle sizes

Methodology Applied

Scientific EffectSintering: Sintering

Data Source

PatentUS11592418B2Solid electrolyte, manufacturing method thereof, and gas sensor

Publication Date: 2023.02.28 DENSO CORP

AI summary

A solid electrolyte includes partially stabilized zirconia in which a stabilizer forms a solid solution in zirconia. The partially stabilized zirconia includes at least monoclinic phase particles and cubic phase particles as crystal particles that configure the partially stabilized zirconia, and an abundance ratio of the monoclinic phase particle is 5 to 25% by volume. The partially stabilized zirconia includes stabilizer low-concentration phase particles of which concentration of the stabilizer at a particle center is equal to or less than 1 mol %, as the crystal particles. The stabilizer low-concentration phase particles have a particle-size distribution of number frequency thereof having a peak at which an average particle size is 0.6 to 1.0 μm, and a particle size at 10% of a cumulative number is 0.5 μm or greater, and of the overall low-concentration phase particles, 50% by volume or greater belong to the peak.