Core-Shell MLCC Dielectric Structure for High Capacitance Stability
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Solution Overview
Problem
Existing multi-layered ceramic capacitors (MLCCs) face challenges in achieving both high capacitance and size miniaturization due to limitations in controlling the microstructure during the sintering process, particularly in improving the dielectric constant and temperature stability of BaTiO3-based materials.
Innovation Solution
A multi-layered capacitor design with dielectric crystal grains comprising a core of BaTiO3, a first shell doped with Sr, Ca, Bi, K, or Na, and a second shell coated with Nb or Ta, achieving a distinct concentration gradient through TEM-EDX analysis, resulting in reduced grain size and enhanced dielectric constant and temperature stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of layers in the body portion is increased to achieve high capacitance, then the capacitance increases, but the device size increases and miniaturization becomes difficult
Solution Approach 1:
The patent changes the chemical composition parameters of the dielectric material by introducing a multi-component system (Ba, Sr, Ca, Ti, Zr, Hf, Nb, Ta) with specific molar ratios. This compositional parameter change enables higher dielectric constant, allowing fewer layers to achieve the same capacitance, thus reducing device size while maintaining high capacitance
Solution Approach 2:
The patent creates a composite dielectric material combining multiple metal oxides (BaTiO3, SrTiO3, CaTiO3, ZrTiO4, HfTiO4, Nb2O5, Ta2O5) in a synergistic composition. This composite material achieves superior dielectric properties with lower loss and higher stability, enabling high capacitance in miniaturized structures
2Stability of the object's composition
If dopants are added to improve temperature stability, then temperature stability improves, but the dielectric constant decreases
Solution Approach 1:
The patent applies different dopants at different locations within the dielectric structure - using Sr and Ca as A-site dopants for temperature stability while incorporating Nb and Ta as B-site dopants to maintain high dielectric constant. This spatial differentiation of dopant functions resolves the trade-off between stability and capacitance
Solution Approach 2:
The patent merges multiple doping functions into a single compositional system where Sr/Ca provide temperature stability and Nb/Ta simultaneously contribute to dielectric constant enhancement. This combined approach eliminates the need to choose between stability and capacitance, achieving both objectives concurrently
3Quantity of substance
If the crystallinity of BaTiO3 is increased to achieve high dielectric constant, then the dielectric constant improves, but the microstructure control during sintering becomes difficult
Solution Approach 1:
The patent modifies the sintering parameters (temperature, time, atmosphere) and compositional parameters (dopant concentrations, raw material ratios) to achieve optimal crystallinity. The multi-component composition buffers against microstructure variations, making the sintering process more controllable while maintaining high dielectric constant
Solution Approach 2:
The patent uses specific dopants (Nb, Ta) as intermediaries that facilitate controlled crystal growth during sintering. These dopants act as nucleation sites and grain growth modifiers, enabling better microstructure control while promoting the formation of highly crystalline phases with superior dielectric properties
Data Source
AI summary
A multi-layered capacitor including a capacitor body including a dielectric layer and an internal electrode; and an external electrode disposed on an outer side of the capacitor body, wherein the dielectric layer includes a plurality of dielectric crystal grains, and the dielectric crystal grains include a core containing BaTiO3, a first shell disposed on the core and containing BaTiO3 doped with a first doping element of Sr, Ca, Bi, K, Na, or a combination thereof, and a second shell disposed on the first shell and containing a first coating element of Nb, Ta, or a combination thereof.