Dielectric Ceramic Composition Gradient Aluminum Distribution
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Solution Overview
Problem
Multilayer ceramic capacitors using reduction-resistant dielectric materials face issues with significant insulation resistance decline under electric fields, short IR lifetime, and poor temperature stability, particularly in extreme temperature conditions, limiting their reliability and practical use in applications like engine control units and anti-lock brake systems.
Innovation Solution
A dielectric ceramic composition with barium titanate as the main component, where the aluminum concentration gradually decreases from the particle surface to the interior, forming an Al non-dispersed region at the center and an Al dispersed region towards the surface, along with specific subcomponents, enhances TC bias characteristics and IR temperature dependency while maintaining high specific permittivity and capacity-temperature characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If uniform Al concentration is maintained throughout the dielectric particles, then high specific permittivity is achieved, but TC bias characteristics and IR temperature dependency deteriorate
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the particle center has low Al concentration (reduction-resistant) and the surface has high Al concentration (oxidation-resistant). This gradient distribution allows the particle core to maintain reduction resistance while the surface layer prevents excessive oxidation, thereby improving both IR lifetime and insulation resistance simultaneously
Solution Approach 2:
The patent uses parameter changes by varying the Al concentration parameter from the particle center to surface. The Al concentration is low at the center (improving TC bias characteristics) and increases toward the surface (improving IR temperature dependency). This parameter gradient resolves the contradiction between uniform Al distribution and performance characteristics
2Reliability
If base metals like Ni are used as conductive material, then cost is reduced, but the internal electrode layers oxidize during firing requiring reducing atmosphere
Solution Approach 1:
The patent creates an inert environment by forming an Al-rich surface layer on the dielectric particles that acts as a protective barrier. This surface layer prevents oxygen from reaching the internal electrode layers during firing, effectively creating a local inert environment that protects the base metal electrodes from oxidation without requiring a reducing atmosphere
Solution Approach 2:
The patent uses the Al-rich surface layer as an intermediary between the dielectric particle core and the external environment. This surface layer mediates the interaction by blocking oxygen diffusion to the internal electrode layers, thereby protecting them from oxidation during firing in air or neutral atmosphere
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 composition improves TC bias characteristics and IR temperature dependency, enabling capacitors to meet X7R or X8R standards, ensuring stable performance across a wide temperature range and extending the IR lifetime, thus enhancing the reliability and practicality of multilayer ceramic capacitors.
Implementation Method 1
a dielectric ceramic composition comprising a main component including barium titanate and an oxide of Al
Implementation Method 2
the IR lifetime is short and the reliability is low
Data Source
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AI summary
A dielectric ceramic composition comprising a main component including barium titanate and an oxide of A1, wherein the dielectric ceramic composition includes a plurality of dielectric particles, concentration of A1 in each of the dielectric particles becomes lower from a particle surface to inside thereof, and each of the dielectric particles has an Al non-dispersed region substantially not including Al at least at a center portion of the particle.