Dielectric Ceramic Composition for High-Temperature Load Life
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Solution Overview
Problem
Dielectric ceramic layers with reduced thickness in laminated ceramic capacitors face challenges in maintaining high-temperature load life when subjected to high electric fields, due to the formation of heterogeneous-phases that can decrease reliability.
Innovation Solution
A dielectric ceramic composition with a perovskite-type compound of barium titanate, containing Ca and a rare-earth element, where the ratio of second heterogeneous-phase grains to total heterogeneous-phase grains is controlled to 0.05 or less, ensuring a higher abundance of first heterogeneous-phase grains with Ca, which improves high-temperature load life under high electric fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If dielectric ceramic layers are reduced in thickness to increase capacitance, then the capacitance increases, but the high-temperature load life decreases due to increased electric field and formation of heterogeneous-phases
Solution Approach 1:
The patent changes the chemical composition parameters of the dielectric ceramic by adding specific amounts of Ca (0.01-0.10 mol ratio relative to BaTiO3) and rare-earth elements (0.01-0.05 mol ratio relative to BaTiO3). This composition modification alters the phase formation behavior during sintering, promoting the formation of beneficial heterogeneous phases (Ca-containing perovskite and rare-earth silicate) while suppressing harmful phases, thereby maintaining high-temperature load life even when layer thickness is reduced to 1 μm or less.
Solution Approach 2:
The patent creates a composite microstructure within the dielectric ceramic by intentionally forming multiple phases: the main perovskite phase (BaTiO3-based), Ca-containing perovskite phase, and rare-earth silicate phase. This composite material approach allows the different phases to work synergistically - the main phase provides dielectric properties, while the heterogeneous phases improve high-temperature stability and suppress oxygen vacancy movement, thus resolving the contradiction between thinness and reliability.
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 dielectric ceramic achieves a favorable high-temperature load life even under high electric fields of 20 kV/mm, maintaining reliability and preventing premature degradation of dielectric layers.
Implementation Method 1
main-phase grains including a perovskite-type compound containing Ba, Ca, and Ti
Implementation Method 2
dielectric ceramic layers have been also progressively reduced in thickness
Implementation Method 3
an interfacial grain boundary phase and a triple-point grain boundary phase formed by the main crystal grains
Data Source
AI summary
A dielectric ceramic that contains, as its main constituent, main-phase grains including a perovskite-type compound containing Ba, Ca, and Ti; first heterogeneous-phase grains containing Ca, a rare-earth element, and Si; and second heterogeneous-phase grains containing no Ca and containing the rare-earth element and Si. The second heterogeneous-phase grains are present in the dielectric ceramic in a ratio of 0.05 or less (including 0) of the number of the second heterogeneous-phase grains to the total of the first heterogeneous-phase grains and the second heterogeneous-phase grains. In the first heterogeneous-phase grains, the content of Ca is preferably 8% or more in terms of molar ratio with respect to the total content of Ca, the rare-earth element, and Si.