Multilayer Ceramic Capacitor Core-Shell Dielectric for High-Temperature Stability
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Solution Overview
Problem
Multilayer ceramic capacitors with dielectric layers containing barium titanate face challenges in maintaining high dielectric constant, temperature stability, and reliability under high AC voltage and temperature loads, particularly when dielectric layer thickness is reduced.
Innovation Solution
The use of dielectric ceramics with a specific composition containing barium titanate, magnesium, vanadium, manganese, rare earth elements, and terbium, which form a solid solution to create a core-shell structure, enhancing the dielectric properties and increasing the curie temperature to 110-120°C, thereby improving the capacitor's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the dielectric layer thickness is reduced to increase capacity and reduce size, then the number of layers can be increased and device size reduced, but the life characteristics in high temperature load test sharply decrease
Solution Approach 1:
The patent changes the chemical composition parameters of the dielectric ceramic by adding specific amounts of magnesium (0.1-0.5 mol), vanadium (0.01-0.1 mol), manganese (0.1-0.5 mol), and rare earth elements (0.1-0.5 mol) to barium titanate (100 mol). This compositional parameter change modifies the crystal structure and dielectric properties, enabling thin dielectric layers to maintain high reliability under temperature stress while achieving increased capacity through reduced layer thickness.
Solution Approach 2:
The patent creates a composite dielectric material system by combining barium titanate with multiple dopants (magnesium, vanadium, manganese, and rare earth elements). This composite structure forms a core-shell configuration where the dopants concentrate at grain boundaries, providing both high dielectric constant and improved thermal stability, thus resolving the contradiction between thin-layer capacity and high-temperature reliability.
2Quantity of substance
If dielectric ceramics containing barium titanate are used to achieve high dielectric constant, then capacity increases, but temperature characteristics stability and AC voltage dependence improve only with specific compositional control
Solution Approach 1:
The patent precisely controls the molar ratios of multiple components in the dielectric ceramic composition. By adjusting the amounts of magnesium (0.1-0.5 mol), vanadium (0.01-0.1 mol), manganese (0.1-0.5 mol), and rare earth elements (0.1-0.5 mol) relative to barium titanate (100 mol), the patent optimizes both the dielectric constant and temperature stability, achieving a balance between high capacity and compositional stability across temperature ranges.
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 results in a multilayer ceramic capacitor with a high relative dielectric constant, low dielectric loss, and improved temperature characteristics, along with increased reliability and reduced AC voltage dependence, ensuring stability in high temperature load tests.
Implementation Method 1
oxide powder of magnesium or rare earth elements are added to barium titanate powder to form a solid solution of the magnesium or the rare earth elements near the surface of the crystal grains containing barium titanate as the main ingredients
Implementation Method 2
the core portion is occupied by a tetragonal crystal phase and, in contrast, the shell portion is occupied by a cubic crystal phase
Data Source
AI summary
Disclosed is a multilayer ceramic capacitor which is formed by alternately laminating (i) dielectric layers composed of a dielectric ceramic and (ii) internal electrode layers. The dielectric ceramic is composed of crystal grains mainly composed of barium titanate, while containing predetermined amounts of magnesium, vanadium, manganese and terbium, and at least one rare earth element selected from yttrium, dysprosium, holmium and erbium. In an x-ray diffraction chart of the dielectric ceramic, the diffraction intensity of the (200) plane indicating cubic barium titanate is higher than the diffraction intensity of the (002) plane indicating tetragonal barium titanate. The dielectric ceramic has a Curie temperature of 110-120° C.