Dielectric Ceramic Composition for DC-Bias Stability
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Solution Overview
Problem
Ferroelectric materials used in multilayer ceramic capacitors exhibit reduced permittivity over time and when subjected to a direct current (DC) electric field, limiting their application in high capacitance devices, especially under DC voltage conditions.
Innovation Solution
A dielectric ceramic composition comprising a base powder of xSrTiO3-(1−x)BiMO3 (M includes Mg and Ti) with a first sub-component of Mn, V, Cr, Fe, Ni, Co, Cu, or Zn, and a second sub-component of Si or a glass compound, which maintains high permittivity and stability under DC electric fields, preventing permittivity reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ferroelectric material based on barium titanate is used to achieve high permittivity at room temperature, then high capacitance is obtained, but permittivity is reduced when DC electric field is applied and over time
Solution Approach 1:
The patent uses a composite material system consisting of BaTiO3 ferroelectric phase combined with paraelectric phases (such as SrTiO3, PbZr1-xTixO3) to create a material that exhibits both high permittivity and stability under DC electric fields. The composite structure allows the ferroelectric phase to provide high capacitance while the paraelectric phase maintains permittivity stability when DC field is applied.
Solution Approach 2:
The patent modifies the chemical composition parameters by adjusting the ratios of BaTiO3 to paraelectric phases, controlling particle size distribution, and optimizing sintering conditions to achieve a balance between high permittivity and DC-field stability. Specific compositional ranges are defined to optimize the contradiction between capacitance and reliability.
2Reliability
If paraelectric material is used to maintain constant permittivity under DC electric field, then permittivity stability is improved, but permittivity is lower than ferroelectric material
Solution Approach 1:
The patent creates a composite material where paraelectric phases (providing DC-field stability) are combined with ferroelectric BaTiO3 phase (providing high permittivity). The synergistic effect of the composite allows achieving both high permittivity and stability under DC fields, overcoming the limitation of using pure paraelectric materials.
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 composition ensures high capacitance without permittivity reduction, even under increased DC electric fields, with a permittivity of 1000 or more at room temperature and minimal change in dielectric constant, enhancing DC-bias characteristics and high-temperature withstand voltage.
Implementation Method 1
a paraelectric material having no change in permittivity when a DC electric field is gradually increased
Data Source
AI summary
There are provided a dielectric ceramic composition and a multilayer ceramic capacitor including the same. The dielectric ceramic composition according to embodiments of the present disclosure includes a base powder represented by xSrTiO3-(1−x)BiMO3 (M includes Mg and Ti) containing a first main component represented by SrTiO3 and a second main component represented by BiMO3, wherein x satisfies 0.5≦x≦0.9.