Dielectric Ceramic Composition for High-Temperature MLCC Stability
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Solution Overview
Problem
Multilayer ceramic capacitors with low Curie temperatures are unsuitable for high-temperature applications, particularly in automobile environments, due to poor static capacitance-temperature characteristics, which limits their stability and reliability at temperatures above 175°C.
Innovation Solution
A dielectric ceramic composition with a perovskite type compound (Ba1-x-yCaxSny)m(Ti1-zZrz)O3, where x, y, and z are within specific ranges, and including rare earth elements and other accessory components, ensures a Curie temperature of 130°C or more and stable dielectric properties, satisfying X9R characteristics up to 175°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dielectric ceramic with low Curie temperature is used, then the dielectric constant increases rapidly with temperature, but the capacitor cannot be used in high temperature region
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition ratios of Ba, Sn, Ti, and rare earth elements in the perovskite ceramic, along with controlling sintering temperature and atmosphere parameters, to achieve a Curie temperature of 130°C or higher while maintaining desired dielectric properties
Solution Approach 2:
The patent uses composite materials by combining barium titanate base ceramic with tin oxide and rare earth element oxides (such as La2O3, Sm2O3, Nd2O3) to create a composite perovskite structure that achieves both high Curie temperature and stable dielectric characteristics at elevated temperatures
2Stability of the object's composition
If Sn is located in Ti site as tetravalent cationic element, then the ceramic structure is stable, but the Curie temperature decreases to room temperature or less
Solution Approach 1:
The patent changes the oxidation state parameter of Sn from tetravalent to divalent, and controls the sintering atmosphere (oxygen partial pressure) to maintain Sn in the +2 oxidation state, which enables Sn to occupy Ba sites and increase Curie temperature while maintaining structural stability through the perovskite crystal structure
3Temperature
If the Curie temperature is increased to 130°C or more, then the capacitor can be used at high temperature, but the static capacitance-temperature characteristics may not satisfy X9R at approximately 175°C
Solution Approach 1:
The patent fine-tunes multiple parameters including the ratios of Ba to Sn, the selection and amount of rare earth elements (0.01-5 mol% relative to BaTiO3), and sintering conditions to achieve an optimal balance where Curie temperature is 130°C or higher while the dielectric constant variation remains within ±15% from -55°C to 175°C, satisfying X9R characteristics
Data Source
AI summary
A dielectric ceramic is provided which is can be stably used for a multilayer ceramic capacitor even at a high temperature of approximately 175° C. The dielectric ceramic includes a perovskite type compound represented by the composition formula (Ba1-x-yCaxSny)m(Ti1-zZrz)O3 (where x, y, z, and m satisfy 0≦x≦0.20, 0.02≦y≦0.20, 0≦z≦0.05, and 0.990≦m≦1.015, respectively) as a primary component; and RE as an accessory component (where RE is at least one selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), wherein 0.5 to 20 molar parts of RE is contained with respect to 100 molar parts of the primary component.