Core-Shell Dielectric Composition for MLCC Temperature Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Multilayer ceramic capacitors face challenges in achieving high permittivity and reliability, particularly in maintaining temperature stability and capacitance characteristics due to the growth of large crystal grains during sintering, which affects their performance and reliability.
Innovation Solution
A dielectric composition with a specific formulation containing zirconium (Zr) and a microstructure comprising a core-shell crystal grain configuration, where the first crystal grain has a Zr content of 3.0% or less in the core and 4.0-15.0% in the shell, and a number fraction of 4% or more, is used to enhance permittivity and temperature stability, along with accessory ingredients to adjust sintering temperature and microstructure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If zirconium content is increased to improve permittivity, then permittivity increases, but temperature stability deteriorates
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core region has low Zr content (≤3.0 at %) for temperature stability and the shell region has high Zr content (4.0-15.0 at %) for high permittivity. This spatial differentiation of material properties allows simultaneous achievement of both temperature stability and high permittivity that cannot be obtained with uniform composition.
Solution Approach 2:
The patent uses composite materials by combining Ba(Ti1-xZrx)O3 with different Zr contents to form a multi-phase system. The composite structure includes a core phase with low Zr substitution (x≤0.03) and a shell phase with high Zr substitution (y=0.04-0.15), creating a material that exhibits both temperature stability from the core phase and high permittivity from the shell phase.
2Manufacturing precision
If sintering temperature is increased to improve densification, then densification improves, but crystal grain growth increases causing reliability deterioration
Solution Approach 1:
The patent applies parameter changes by optimizing the sintering temperature range to 950-1050°C, which is lower than conventional sintering temperatures. This temperature parameter change prevents excessive crystal grain growth while achieving sufficient densification, thereby maintaining reliability. The core-shell structure formed at this temperature range provides the necessary densification without the harmful effect of large grain growth.
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 enables the production of multilayer ceramic capacitors with permittivity of 7000 or more, high-temperature withstand voltage of 50V/μm or more, and temperature coefficient of capacitance (TCC) less than ±33% at 85°C, thereby addressing the issues of temperature stability and reliability.
Implementation Method 1
a base material powder composed of Ba(Ti1-xZrx)O3 as a first main ingredient and Ba(Ti1-yZry)O3 as a second main ingredient
Implementation Method 2
a first crystal grain is composed of a core part having a Zr content of 3.0 at % or less and a shell part having a Zr content of 4.0 to 15.0 at %
Implementation Method 3
a multilayer ceramic capacitor is manufactured by stacking layers of a conductive paste for an internal electrode and a dielectric paste using a sheet method, a printing method, or the like, and then sintering the stacked layers of paste
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 outer surfaces of the ceramic body, wherein the dielectric layer contains zirconium (Zr), a Zr content is 2×Zr/(Ba+Ca+Ti+Zr) based on an atomic ratio, a first crystal grain is composed of a core part having a Zr content of 3.0 at % or less and a shell part having a Zr content of 4.0 to 15.0 at %, and a number fraction of the first crystal grain to all crystal grains in the dielectric layer is 4% or more.