Dielectric Composition With Al-Si-O Grain Boundaries Against Cracks
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Solution Overview
Problem
Multilayer ceramic electronic devices experience structural defects such as cracks due to differences in characteristics between ceramic and internal electrode layers, leading to reduced durability in high-temperature and high-humidity environments.
Innovation Solution
A dielectric composition comprising dielectric particles with a perovskite compound, grain boundary phases, and segregations containing Al, Si, and O, with a molar ratio of Al/(Al+Si) between 0.45 and 0.75, enhances joint strength between particles, preventing crack growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multilayer ceramic electronic devices are formed by alternately laminating ceramic layers and internal electrode layers, then the device structure is achieved, but structural defects such as cracks occur due to differences in shrinkage factor and linear expansion coefficient between layers
Solution Approach 1:
The patent applies local quality by creating segregations with specific Al-Si-O composition at the grain boundaries between dielectric particles. These segregations are localized at critical interfaces where crack propagation is most likely to occur, providing targeted reinforcement without altering the bulk material properties. The segregations have a controlled Al/(Al+Si) molar ratio of 0.45-0.75, creating a chemically distinct zone that strengthens the grain boundary region specifically.
Solution Approach 2:
The patent employs composite materials by forming a multi-phase structure consisting of dielectric particles (perovskite compound), grain boundary phases, and Al-Si-O segregations. This composite structure combines the dielectric properties of the perovskite particles with the strengthening effect of the Al-Si-O segregations at the grain boundaries, creating a material that exhibits both functional and mechanical superiority.
2Reliability
If ceramic layers are composed of dielectric composition, then the dielectric function is achieved, but cracks occur due to characteristic differences with internal electrode layers
Solution Approach 1:
The patent applies beforehand cushioning by pre-forming Al-Si-O segregations at the grain boundaries before the device is subjected to thermal and mechanical stress. These segregations act as preventive measures that cushion against crack initiation and propagation. The segregations are created during the sintering process, providing proactive protection against the harmful effects of thermal expansion mismatch and shrinkage differences that will occur during device operation.
3Strength
If grain boundary phases are present between dielectric particles, then the dielectric composition is complete, but crack growth can occur reducing durability
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition of the grain boundary segregations, specifically the Al/(Al+Si) molar ratio, within the range of 0.45-0.75. This parameter optimization ensures that the segregations have the optimal balance of strength and compatibility with the dielectric particles. The specific composition range is determined to maximize crack resistance while maintaining the dielectric properties of the material.
Data Source
AI summary
A dielectric composition includes dielectric particles, grain boundary phases, and segregations. The dielectric particles each include a perovskite compound represented by ABO3 as a main component. The grain boundary phases are located between the dielectric particles. The segregations exist in a part of the grain boundary phases and include at least Al, Si, and O. A molar ratio (Al/(Al+Si)) of an Al content to a total content of Al and Si in the segregations is 0.45 or more and 0.75 or less.