Multilayer Ceramic Capacitor Grain Boundary Ion Radius Control
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Solution Overview
Problem
Multilayer ceramic capacitors face reliability issues due to uneven ceramic structures caused by excessive grain growth and local electric field concentrations when DC voltage is applied, resulting from the replacement of Ba2+ with Re3+ ions, which affects the movement of oxygen vacancies and ion radius differences.
Innovation Solution
A multilayer electronic component with dielectric layers containing a perovskite-type compound of Ba, a first rare earth element (e.g., Gd), and a second rare earth element (e.g., Dy) is developed, where the difference in ion radii between the rare earth elements is controlled to form stable vacancy pairs with oxygen vacancies, preventing excessive Ba vacancy formation and grain growth, thereby maintaining structural uniformity and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the ion radius of Re3+ is close to that of Ba2+, then the replacement of Ba2+ with Re3+ becomes easier during sintering, but excessive Ba vacancies are formed causing excessive grain growth and uneven ceramic structure
Solution Approach 1:
The patent changes the ionic radius parameter by selecting Re3+ ions with different radii (Gd3+: 1.053Å, Dy3+: 1.027Å, Ho3+: 1.015Å) to optimize the replacement process. By carefully selecting the ionic radius difference, the patent achieves effective oxygen vacancy suppression without excessive grain growth, resolving the contradiction between ease of replacement and ceramic structure uniformity.
Solution Approach 2:
The patent applies different rare earth elements at different locations within the dielectric layer. Specifically, Re3+ ions are introduced to replace Ba2+ ions in the crystal lattice, creating localized vacancy pairs that pin oxygen vacancies. This local modification of the crystal structure prevents excessive grain growth while maintaining overall ceramic structure uniformity.
2Manufacturing precision
If the ion radius of Re3+ is large compared to Ba2+, then the replacement of Ba2+ with Re3+ is difficult during sintering, but the ceramic structure remains more uniform
Solution Approach 1:
The patent optimizes the ionic radius parameter by selecting Re3+ ions with specific radii (1.015-1.053Å) that are smaller than Ba2+ (1.42Å) but not excessively so. This parameter optimization enables sufficient replacement during sintering while maintaining ceramic structure uniformity, resolving the contradiction between ease of replacement and structural uniformity.
3Reliability
If excessive replacement of Ba2+ with Re3+ occurs, then oxygen vacancy movement is suppressed, but excessive Ba vacancies cause easy grain growth and local electric field concentration
Solution Approach 1:
The patent changes the concentration parameter by controlling the amount of Re3+ ions introduced into the dielectric layer. By optimizing the replacement ratio (not exceeding certain limits), the patent achieves sufficient oxygen vacancy suppression without creating excessive Ba vacancies that would lead to grain growth and electric field concentration, thus resolving the contradiction between reliability improvement and harmful factor suppression.
Solution Approach 2:
The patent converts the potential harm of Ba vacancies into a benefit by controlling their formation. Instead of preventing all Ba vacancies, the patent allows controlled formation of vacancy pairs that pin oxygen vacancies, while preventing excessive grain growth. This transforms the harmful effect into a useful mechanism for suppressing oxygen vacancy movement without creating local electric field concentration.
4Stability of the object's composition
If Re3+ is locally present in grain boundaries, then the ceramic structure may be stable, but local electric field concentration occurs when DC voltage is applied
Solution Approach 1:
The patent applies local quality by distributing Re3+ ions uniformly throughout the dielectric layer rather than allowing them to concentrate in grain boundaries. This uniform distribution prevents local electric field concentration while maintaining ceramic structure stability, resolving the contradiction between structural stability and harmful factor suppression.
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 controlled ion radius difference between the rare earth elements effectively reduces oxygen vacancy movement and local electric field concentrations, enhancing the reliability of the multilayer ceramic capacitors by maintaining a stable ceramic structure during voltage application.
Implementation Method 1
replace Ba2+, which is a positive divalent ion of Ba in a crystal lattice of BaTiO3, with Re3+, which is a positive trivalent ion of rare earth element Re
Implementation Method 2
These Ba vacancies form stable vacancy pairs with oxygen vacancies that can be regarded as being relatively positive-divalently charged
Implementation Method 3
As a difference between an ion radius of Ba2+ and an ion radius of Re3+ becomes smaller, the replacement of Ba2+ with Re3+ becomes easier during sintering of the dielectric layers
Implementation Method 4
during sintering of the dielectric layers, the BaTiO3 particles become more active on the surfaces thereof and are readily 'necked' together
Implementation Method 5
When a DC voltage is applied to the dielectric layers, local concentration of the electric field may occur due to the unevenness of the ceramic structure
Data Source
AI summary
A multilayer electronic component having a plurality of stacked dielectric layers and a plurality of internal electrode layers. Each of the dielectric layers has a plurality of crystal grains including a perovskite-type compound containing Ba, a first rare earth element and a second rare earth element. A difference between a positive trivalent ion radius of the first rare earth element and a positive divalent ion radius of Ba is smaller than a difference between a positive trivalent ion radius of the second rare earth element and the positive divalent ion radius of Ba. A sum of an amount of the first rare earth element and the second rare earth element in a first region along a grain boundary is larger than a sum of an amount of the first rare earth element and the second rare earth element in a second region in a center portion of the crystal grain.