Dielectric ceramic and multilayer ceramic capacitor
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Solution Overview
Problem
The challenge is to improve the reliability and capacitance-temperature characteristics of multilayer ceramic capacitors, particularly when subjected to high temperatures and high electric fields, without degrading the permittivity.
Innovation Solution
A dielectric ceramic with a barium titanate (BaTiO3)-based compound as the main component, featuring multiple regions with specific rare earth element concentrations and a controlled rare earth element concentration gradient, is used to form a capacitor with high permittivity, high reliability, and excellent capacitance-temperature characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If firing temperature is increased or reducing atmosphere is used to form high concentration rare earth element solid solution, then reliability is improved, but BaTiO3 grain growth occurs and capacitance-temperature characteristics degrade
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the shell region contains high concentration rare earth element solid solution (formed at lower temperature to prevent grain growth) and the core region contains lower concentration. This spatial differentiation allows the shell to provide reliability improvement through oxygen vacancy suppression while the core maintains capacitance-temperature characteristics by avoiding excessive grain growth.
Solution Approach 2:
The patent segments the crystal grain into two distinct regions: a shell region with high rare earth element concentration and a core region with low rare earth element concentration. This segmentation allows different functional requirements to be met in different regions - the shell provides reliability enhancement while the core preserves dielectric performance.
2Quantity of substance
If dielectric layer thickness is reduced to achieve high capacitance, then capacitance increases, but electric field intensity increases causing oxygen vacancy movement and insulation resistance reduction
Solution Approach 1:
The patent changes the compositional parameter by incorporating rare earth elements into the BaTiO3 lattice structure. This compositional modification alters the electrical properties of the dielectric material, enabling thin dielectric layers to maintain high insulation resistance even under intense electric fields by suppressing oxygen vacancy migration through the rare earth element solid solution effect.
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 proposed solution effectively enhances the reliability and temperature stability of multilayer ceramic capacitors, maintaining high permittivity and capacitance-temperature characteristics even under demanding conditions.
Implementation Method 1
a rare earth element solid solution in a surface portion (shell) of BaTiO3 crystal grains
Implementation Method 2
The rare earth element solid solution can be formed by a process that includes mixing BiTiO3 with a rare earth element compound... The rare earth element solid solution is thought to suppress the movement of oxygen vacancies and thus to increase the reliability (durability)
Implementation Method 3
the core portion exhibiting ferroelectricity can provide high specific permittivity
Implementation Method 4
the DC current applied will flow through the diffusive phase with a low permittivity so that the reduction in insulation resistance can be suppressed
Data Source
AI summary
A dielectric ceramic that includes multiple crystal grains, each of the multiple crystal grains having an interface, a barium titanate (BaTiO3)-based compound as a main component thereof, and a rare earth element. The dielectric ceramic has a cross-section in which the multiple crystal grains has a concentration varying region, a high concentration region, and a low concentration region. The concentration varying region has an RE/Ti ratio differing by 3% or more. The high concentration region has an RE/Ti ratio of 5% to 20%. The low concentration region has an RE/Ti ratio of 0% to 2%.