Dielectric Ceramic Composition for Ni-Electrode LCC
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Solution Overview
Problem
The existing KSr2Nb5O15 ceramic composition used in laminated ceramic capacitors exhibits a high dielectric constant but has insufficient temperature characteristics and insulation resistivity at high temperatures, particularly around 175°C, which is not stable enough to meet the required ±15% capacitance change in the temperature range of −55 to 175°C and lacks sufficient insulation resistivity.
Innovation Solution
A dielectric ceramic composition with a mixed crystal system of (K1-xNax)(Sr1-y-zBayCaz)2Nb5O15 and (Ba1-bCab)TiO3, where a, b, x, y, and z are within specific molar ratios, combined with additional components like V, Mn, Cr, Fe, Co, Ni, Zn, Mg, or Si, to enhance sinterability and maintain high dielectric constant, temperature stability, and insulation resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If KSr2Nb5O15 ceramic composition is used to achieve high dielectric constant, then the dielectric constant is improved, but the temperature characteristics of capacitance and insulation resistivity at high temperature deteriorate
Solution Approach 1:
The patent uses a composite ceramic system combining KSr2Nb5O15 (tungsten bronze structure) with BaTiO3 (perovskite structure) and additional components like SrZr1-xMxO3, SrHf1-xMxO3, or Pb(Zr1-yTiy)O3. This composite approach allows the material to achieve both high dielectric constant (≥2000) and improved temperature characteristics (capacitance change within ±15% from -55 to 175°C) by leveraging the complementary properties of different crystal structures and phase transition behaviors.
Solution Approach 2:
The patent systematically varies compositional parameters including the molar ratio of KSr2Nb5O15 to BaTiO3 (0.3≤a≤0.8), substitution amounts of Ca for Sr (0.1≤y≤0.5), and additional component concentrations to optimize both dielectric constant and temperature stability. By controlling parameters like x, y, z, and b within specific ranges, the invention achieves simultaneous improvement in dielectric performance and high-temperature reliability.
2Force
If KSr2Nb5O15 ceramic composition is used to achieve high dielectric constant, then the dielectric constant is improved, but the insulation resistivity at high temperature deteriorates
Solution Approach 1:
The composite ceramic system incorporates insulating components such as SrZr1-xMxO3, SrHf1-xMxO3, or Pb(Zr1-yTiy)O3 alongside the KSr2Nb5O15-BaTiO3 base system. These additional components form a multi-phase composite that provides both high dielectric constant and high insulation resistivity (log ρ≥8.0 at 175°C) by creating grain boundary effects and reducing ion migration at high temperatures.
Solution Approach 2:
The patent introduces local compositional variations through substitution of Sr with Ca (0.1≤y≤0.5) and addition of specific components at controlled concentrations. This creates local regions with different properties: the bulk provides high dielectric constant while grain boundaries and interfacial regions provide enhanced insulation resistance, achieving both requirements simultaneously.
3Ease of manufacture
If Ni is used as internal electrode material to reduce manufacturing cost, then manufacturing cost is reduced, but oxidation resistance during firing deteriorates
Solution Approach 1:
The dielectric ceramic composition acts as an intermediary protective environment during firing. The specific ceramic composition with controlled atmosphere stability and reduced oxygen partial pressure requirements creates a protective matrix that prevents Ni oxidation while allowing the internal electrodes to be formed. This eliminates the need for additional protective atmospheres or coatings, reducing manufacturing complexity while maintaining cost-effectiveness.
Solution Approach 2:
The patent modifies the firing process parameters by using the specific dielectric ceramic composition that allows firing at temperatures (1200-1400°C) and atmosphere conditions that prevent Ni oxidation. The composition's chemical stability and oxygen buffering capacity enable Ni-based internal electrodes to be formed without severe oxidation, maintaining both cost advantages and electrode integrity.
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 achieves a high dielectric constant, stable temperature characteristics, and sufficient insulation resistivity at 175°C, ensuring the laminated ceramic capacitor's stability in high-temperature environments.
Implementation Method 1
a dielectric ceramic composition whose elemental composition is a mixed crystal system of KSr2Nb5O15 compounds having a tungsten bronze structure and BaTiO3 compounds having a perovskite structure
Implementation Method 2
the capacitance change due to temperature relative to the capacitance at 25° C. (the temperature characteristics of capacitance) needs to be ±15% or less in a temperature range of −55 to 175° C.
Data Source
AI summary
There is provided a dielectric ceramic composition that is a dielectric ceramic material used for a laminated ceramic capacitor; that can be co-fired with internal electrodes mainly composed of Ni at a temperature of 1300° C. or less; and that has a high dielectric constant, good temperature characteristics of capacitance in a range of −55 to 175° C., and a high resistivity ρ at 175° C. The dielectric ceramic composition includes a main component represented by a composition formula (1-a) (K1-xNax)(Sr1-y-zBayCaz)2Nb5O15-a(Ba1-bCab)TiO3 (where a, b, x, y, and z are all molar amounts and 0.3≦a≦0.8, 0≦b≦0.2, 0≦x<0.2, 0.1≦y≦0.5, 0.1≦z≦0.5, and 0.2≦y+z≦0.7); and M, as an additional component, in an amount of 0.1 to 40 parts by mole relative to 100 parts by mole of the main component (where M is at least one element from the group of V, Mn, Cr, Fe, Co, Ni, Zn, Mg, and Si).