Core-Shell Dielectric Composition for Grain-Stable MLCCs
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Solution Overview
Problem
Multilayer ceramic capacitors face challenges in achieving high permittivity without grain growth during sintering, leading to a decrease in capacitance under high electric fields, as grain growth is inevitable due to atomization of dielectric materials.
Innovation Solution
A dielectric composition with a barium titanate-based powder particle featuring a core-shell structure, where titanium in the shell is partially substituted with elements like Sn, Zr, or Hf, ensuring the shell covers at least 30% of the core's surface, which suppresses grain growth and maintains high permittivity during sintering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complete sintering is performed to achieve high capacitance, then permittivity increases, but grain growth occurs leading to decrease in capacitance under high electric field
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the shell has different compositional characteristics than the core. The shell contains titanium substituted with elements (Sn, Zr, Hf) that have the same oxidation number but different ionic radii, creating a localized region with suppressed grain growth capability while maintaining high permittivity. This local structural differentiation allows the grain boundaries to act as barriers without compromising the overall dielectric performance.
Solution Approach 2:
The patent employs composite materials by combining barium titanate base material with substituted elements (Sn, Zr, Hf) in a core-shell configuration. This composite structure integrates materials with different properties: the core provides high permittivity while the shell provides grain growth suppression. The composite nature allows simultaneous achievement of high capacitance and grain size control.
2Shape
If grain growth is suppressed to maintain capacitance, then permittivity decreases due to lack of densification
Solution Approach 1:
The patent applies parameter changes by modifying the ionic radius parameter through substitution of titanium with elements (Sn, Zr, Hf) that have different ionic radii. This substitution in the shell region creates a parameter gradient that suppresses grain growth while the overall composition maintains high permittivity. The controlled parameter variation allows decoupling of grain size control from permittivity maintenance.
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 effectively densifies the dielectric composition, enhancing its withstand voltage characteristics and reliability while maintaining high capacitance, even under DC-bias conditions, by preventing grain growth and increasing permittivity.
Implementation Method 1
the shell having a structure in which titanium is partially substituted with an element having the same oxidation number as that of the titanium in the barium titanate-based powder particle and having an ionic radius different from that of the titanium in the barium titanate-based powder particle
Implementation Method 2
there is a need to develop a dielectric composition capable of being densified even at high temperature, without accompanying grain growth
Data Source
AI summary
A multilayer ceramic capacitor includes: a ceramic body including dielectric layers and first and second internal electrodes disposed to face each other with respective dielectric layers interposed therebetween; and first and second external electrodes disposed on an external surface of the ceramic body, wherein the dielectric layer contains a barium titanate-based powder particle having a core-shell structure including a core and a shell around the core, the shell having a structure in which titanium is partially substituted with an element having the same oxidation number as that of the titanium in the barium titanate-based powder particle and having an ionic radius different from that of the titanium in the barium titanate-based powder particle, and the shell covers at least 30% of a surface of the core.