Dielectric Ceramic Composition for X8R Thermal Stability
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Solution Overview
Problem
Conventional dielectric ceramic compositions for high-capacitance multi-layered ceramic capacitors struggle to maintain high permittivity and thermal stability above the Curie temperature without using harmful lead (Pb) and often result in reduced reliability due to the formation of secondary phases or inadequate temperature coefficient of capacitance (TCC) properties.
Innovation Solution
A dielectric ceramic composition comprising a solid solution of BaTiO3 and (Na, K)NbO3 with added SiO2 and MnO2, sintered at 1300°C or less under reduced atmosphere, which maintains high permittivity and provides X8R thermal properties without Pb, using a nickel internal electrode and specific subcomponents like MnO2 to enhance sinterability and insulation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional dielectric ceramic compositions use BaTiO3 with additive subcomponents (Mg, rare-earth elements) to achieve high capacitance, then permittivity is improved, but thermal stability above Curie temperature deteriorates and reliability reduces due to secondary phase formation
Solution Approach 1:
The patent employs a composite material system consisting of BaTiO3 as the main component combined with specific additive subcomponents (CaO: 0.1-5.0 wt%, Al2O3: 0.1-5.0 wt%, SiO2: 0.1-5.0 wt%, MnO2: 0.1-5.0 wt%). This composite approach allows the material to achieve high permittivity (≥1500 at room temperature) while maintaining thermal stability and X8R properties, resolving the contradiction between permittivity enhancement and thermal reliability
Solution Approach 2:
The patent optimizes the compositional parameters of the dielectric ceramic by precisely controlling the weight percentages of each component. By adjusting the ratios of BaTiO3, CaO, Al2O3, SiO2, and MnO2, the material achieves both high permittivity and stable temperature coefficient of capacitance (TCC) within ±15% from -55°C to +150°C, thereby improving thermal stability without sacrificing permittivity
2Reliability
If rare-earth elements and fixed-valence acceptors (Mg) are added to BaTiO3 to form core-shell structure, then desired capacitor properties are achieved, but sintering temperature must be increased which complicates the manufacturing process
Solution Approach 1:
The patent modifies the compositional parameters by incorporating sintering aid subcomponents (CaO, Al2O3, SiO2, MnO2) that lower the sintering temperature to 1300°C or below. This parameter optimization enables the formation of desired capacitor properties including high permittivity and stable TCC while simplifying the manufacturing process through reduced sintering temperature requirements
3Temperature
If CaZrO3 or excess rare-earth elements are added to BaTiO3 to increase Curie temperature and alleviate reduced permittivity, then thermal properties improve, but the composition complexity and manufacturing difficulty increase
Solution Approach 1:
The patent uses a composite material approach with BaTiO3 combined with CaO, Al2O3, SiO2, and MnO2 subcomponents. This composite system achieves increased Curie temperature and maintained permittivity without requiring complex compositions like CaZrO3 or excess rare-earth elements, thereby improving thermal properties while keeping the composition relatively simple and manufacturable
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 achieves permittivity of 1500 or more at room temperature, a temperature coefficient of capacitance within ±15% of the X8R standard, and withstand voltage of 50 V/μm or more at 150°C, ensuring reliable thermal and voltage-proof performance in electric devices like multi-layered ceramic capacitors.
Implementation Method 1
mixing or forming a solid solution of BaTiO3 and (Na, K)NbO3 in an appropriate ratio
Implementation Method 2
sintered at 1300°C or less under reduced atmosphere
Implementation Method 3
a temperature coefficient of capacitance at 150°C between -15% and +15%
Data Source
AI summary
A dielectric ceramic composition includes a main component comprising (1-x)BaTiO3-x(Na1-yKy)NbO3, where 0.005≦x≦0.5 and 0.3≦y≦1.0; a first subcomponent comprising an element selected from the group consisting of Mn, V, Cr, Fe, Ni, Co, Cu and Zn; and a second subcomponent comprising SiO2.