Multilayer Ceramic Capacitor Volatile Element B-Site Stabilization
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Solution Overview
Problem
Multilayer ceramic capacitors with perovskite-type dielectric layers and base metal internal electrodes face insulation performance degradation over time due to oxygen defects generated during firing in reducing atmospheres, leading to reliability issues under continuous high-temperature operation.
Innovation Solution
Forming a solid solution at the B site of the perovskite-type compound with a volatile element, such as Zn, Sn, or In, and co-firing with base metal internal electrodes under a reducing atmosphere to volatilize and partially fix the volatile element within the electrodes, suppressing oxygen defect diffusion and enhancing insulation performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If firing is performed in a reducing atmosphere to prevent oxidation of base metal internal electrodes, then the internal electrodes maintain their conductivity and structural integrity, but oxygen defects are generated in the perovskite-type dielectric layers which diffuse during operation and degrade insulation performance over time
Solution Approach 1:
A volatile element (Zn, Sn, or In) is introduced as an intermediary substance during the firing process. This element temporarily occupies B sites in the perovskite structure and suppresses oxygen defect formation. During subsequent heating, the volatile element evaporates, leaving behind a stabilized crystal structure with reduced oxygen defects that would otherwise degrade insulation performance
Solution Approach 2:
The chemical composition parameters of the perovskite-type compound are modified by incorporating a volatile element at the B site. This compositional change alters the firing behavior and oxygen defect characteristics of the dielectric layer, enabling stable insulation performance when fired in a reducing atmosphere required for base metal electrode preservation
2Reliability
If a volatile element is incorporated at the B site to suppress oxygen defect diffusion, then insulation performance stability is improved, but the volatile element may evaporate excessively during firing leading to loss of dielectric properties
Solution Approach 1:
The amount of volatile element is precisely controlled within the range of 0.01 to 0.20 mole ratio relative to A site elements. This parameter optimization ensures sufficient volatile element remains to suppress oxygen defect diffusion while allowing enough to evaporate and form the desired stabilized structure without excessive loss of dielectric properties
Solution Approach 2:
The volatile element is introduced in an amount that is partially consumed during firing to suppress oxygen defects, with the understanding that some evaporation is necessary and beneficial. The amount is controlled to be excessive enough to ensure sufficient suppression of oxygen defects but not so excessive as to cause permanent structural degradation
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 suppresses insulation performance degradation over time, ensuring reliable operation even at high temperatures by synergistically improving the interface insulation between dielectric layers and internal electrodes, thus enhancing the high-temperature load lifetime of multilayer ceramic capacitors.
Implementation Method 1
a main constituent of each of the dielectric layers is formed from a perovskite-type compound represented by the general formula ABO3, and the perovskite-type compound contains at least Ti and a volatile element that forms a solid solution at a B site
Implementation Method 2
co-firing with base metal internal electrodes under a reducing atmosphere to volatilize and partially fix the volatile element within the electrodes
Implementation Method 3
it is necessary to perform a firing treatment in a reducing atmosphere where the base metal material is not oxidized
Data Source
AI summary
A multilayer ceramic capacitor having a ceramic sintered body with alternately laminated dielectric layers and internal electrodes. The dielectric layers are formed from a perovskite-type compound represented by the general formula ABO3, and the perovskite-type compound contains at least Ti and a volatile element that forms a solid solution at a B site thereof. The internal electrodes are formed from a base metal material and contain the volatile element. The content of the volatile element is greater than 0 parts by mole and less than or equal to 0.2 parts by mole with respect to 100 parts by mole of the constituent element at the B site, and excluding the volatile element at the B site.