Aligned Crystal Orientation in BaTiO3 Dielectric Ceramic
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Solution Overview
Problem
Laminated ceramic capacitors experience a significant decrease in dielectric constant when the applied voltage is reduced, making them unsuitable for low-voltage applications due to their homogeneous composition and crystal system.
Innovation Solution
A dielectric ceramic with a perovskite-type compound, primarily BaTiO3, where the crystal orientations within the crystal grains are aligned in the same direction, enhancing stability and AC electric field characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a homogeneous dielectric ceramic material is used to achieve high dielectric constant, then the dielectric constant is improved, but the dielectric constant significantly decreases when applied voltage is reduced
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the crystal grain interior (core) and surface layer (shell) have different compositions and properties. The core contains BaTiO3 with specific crystal orientation for high dielectric constant, while the shell has modified composition to maintain stability under varying voltage conditions. This local differentiation resolves the contradiction by allowing the core to provide high dielectric constant while the shell ensures voltage stability.
Solution Approach 2:
The patent uses composite materials by combining BaTiO3-based dielectric ceramic with specific additives (such as rare earth elements like Dy, Y, or Nd) to create a multi-phase structure. This composite approach allows the material to exhibit both high dielectric constant from the BaTiO3 phase and improved voltage stability from the additive-modified phases, particularly at grain boundaries and surface layers.
2Ease of manufacture
If homogeneous composition throughout crystal grains is used to facilitate improvement in dielectric constant, then manufacturing is simplified, but AC electric field characteristics deteriorate at low voltages
Solution Approach 1:
The patent implements local quality by introducing compositional gradients within crystal grains, where the core region has one composition and the surface layer has another. This allows the material to exhibit different properties in different regions: the core provides ease of manufacture through standard sintering processes, while the surface layer with modified composition (containing specific additives) provides adapted AC electric field characteristics for low-voltage applications.
Solution Approach 2:
The patent applies parameter changes by systematically varying the composition parameters (additive types and concentrations) in the surface layer compared to the core. By controlling parameters such as rare earth element content (0.1-5 wt%) and sintering conditions, the material achieves both manufacturing feasibility and optimized AC electric field characteristics across different voltage ranges.
3Reliability
If crystal orientations are aligned in the same direction within crystal grain to improve AC electric field characteristics, then dielectric constant stability under voltage change is improved, but manufacturing complexity increases
Solution Approach 1:
The patent utilizes phase transitions during the sintering process to achieve aligned crystal orientations. By controlling the heating schedule and sintering atmosphere, the material undergoes phase transformations that naturally promote texture formation and crystal orientation alignment. This approach improves dielectric constant stability under voltage change while avoiding overly complex manufacturing processes, as the alignment is achieved through thermodynamic phase evolution rather than mechanical manipulation.
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 aligned crystal orientations in the dielectric ceramic result in improved AC electric field characteristics and stable capacitance performance even at low voltages, reducing the variation in dielectric constant and enhancing the capacitive performance of laminated ceramic capacitors.
Implementation Method 1
The BaTiO3 is a ferroelectric, and large numbers of core-shell structures and the like have been found in which an additive is dispersed only in the vicinity of surface layers of the crystal grains
Implementation Method 2
a dielectric ceramic which has a high dielectric constant and has favorable AC electric field characteristics in which the change in dielectric constant is small even with changes in an AC electric field can be obtained when crystal orientations in the crystal grains are aligned within the crystal grain
Data Source
AI summary
In a dielectric ceramic having crystal grains and containing a perovskite in which the A site contains Ba and the B site contains Ti. as a main component, the crystal orientations are aligned in substantially the same direction within the crystal grains. Some of Ba may be replaced with Ca and/or Sr, and some of Ti may be replaced with Zr and/pr Hf. This achieves a dielectric ceramic which has a high dielectric constant and has favorable AC electric field characteristics in which the change in dielectric constant is small even with changes in applied electric field.