Perovskite Dielectric Core-Shell Structure for Oxygen Vacancy Control
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Solution Overview
Problem
Ceramic electronic devices face reduced lifetime due to oxygen vacancies formed in reductive atmospheres during firing, which degrade under high-temperature loads and re-oxidation processes, especially in core regions with low additive concentrations.
Innovation Solution
Implementing a core-shell structure in dielectric layers with a perovskite ceramic material, where the dispersion and direction of atomic displacement between B site atoms and oxygen atoms in the shell differ from those in the core, enhancing the suppression of oxygen vacancy diffusion and accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If firing is performed in a reductive atmosphere to prevent oxidation of metal internal electrodes, then oxidation resistance is improved, but oxygen vacancies are formed in the ceramic dielectric layers which degrade lifetime under high-temperature load
Solution Approach 1:
The crystal grain is divided into core and shell regions with different compositions and structures. The core region contains the main perovskite ceramic material, while the shell region contains a different phase or composition that suppresses oxygen vacancy formation and movement, thereby resolving the contradiction between maintaining reducing atmosphere for electrode protection and preventing oxygen vacancies in the dielectric
Solution Approach 2:
Different regions of the ceramic dielectric layer are given different properties: the core region maintains the perovskite structure for dielectric function, while the shell region has modified composition or phase that specifically targets oxygen vacancy suppression. This local differentiation allows the device to withstand reductive firing conditions without forming harmful oxygen vacancies at grain boundaries
2Duration of action of stationary object
If a re-oxidation process is performed at low temperature in oxidizing atmosphere to reduce oxygen vacancies, then oxygen vacancy amount is reduced, but the metal internal electrodes may be oxidized
Solution Approach 1:
The core-shell structure is formed in advance during the main firing process, creating a protective shell region that prevents oxygen vacancy formation before any re-oxidation process could occur. This preliminary structural preparation eliminates the need for subsequent re-oxidation treatments that would risk oxidizing the metal electrodes
Solution Approach 2:
The shell region, which could be seen as an added complexity, actually serves as a protective barrier that converts the potentially harmful oxidizing atmosphere into a beneficial effect by preventing oxygen from reaching and oxidizing the metal internal electrodes while still allowing oxygen vacancy suppression
3Duration of action of stationary object
If the dispersion of atomic displacement in the shell is increased to suppress oxygen vacancy diffusion, then lifetime is improved, but the structural complexity of the crystal grain increases
Solution Approach 1:
The complexity is localized only to the shell region surrounding each crystal grain, while the core region maintains a simple perovskite structure. This localized approach achieves oxygen vacancy suppression without requiring complex structures throughout the entire ceramic material, balancing performance improvement with manufacturing feasibility
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
This approach improves the lifetime of ceramic electronic devices by reducing oxygen vacancy movement and accumulation, even under re-oxidation processes in strong reductive atmospheres, thereby maintaining performance and reliability.
Implementation Method 1
an oxygen vacancy formed in the ceramic in the firing process in the reductive atmosphere degrades a lifetime in a high-temperature load test
Data Source
AI summary
A ceramic electronic device includes a multilayer structure in which each of a plurality of dielectric layers and each of a plurality of internal electrode layers are alternately stacked, a main component of the plurality of dielectric layers being a ceramic having a perovskite structure expressed by a general formula ABO3. At least one of crystal grains of the plurality of dielectric layers has a core-shell structure. A dispersion of atomic displacement amounts between B site atoms and oxygen atoms of a shell of the core-shell structure is larger than a dispersion of atomic displacement amounts between B site atoms and oxygen atoms of a core of the core-shell structure.