Dielectric Ceramic Composition for High-Temperature Monolithic Capacitors
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Solution Overview
Problem
Current dielectric ceramic compositions for high-temperature monolithic ceramic capacitors face challenges in maintaining reliability and a flat temperature-dependent change rate of the relative dielectric constant, especially when subjected to high DC current field strengths at elevated temperatures, such as in car environments.
Innovation Solution
A dielectric ceramic composition with a formula of 100(Ba1-xCax)TiO3+aR2O3+bV2O5+cZrO2+dMnO, where R is a specific metal element and the mole values satisfy certain conditions, is used to create a sintered compact with a larger relative dielectric constant and reduced temperature-dependent change rate, enhancing the capacitor's reliability and life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amount of added Re is increased to improve reliability, then the reliability is improved, but the temperature-dependent change rate of the relative dielectric constant is degraded
Solution Approach 1:
The patent changes the chemical composition parameters by introducing ZrO2 as a new component and optimizing the ratios of existing components (Ba1-xCax)TiO3, R2O3, V2O5, and MnO. This compositional parameter adjustment allows achieving both high reliability and flat temperature-dependent change rate of the relative dielectric constant, resolving the contradiction between reliability improvement and temperature stability degradation that occurred when simply increasing Re content.
Solution Approach 2:
The patent creates a composite dielectric ceramic material combining multiple oxides: (Ba1-xCax)TiO3 as the base, R2O3 (rare earth oxide), V2O5 (vanadium oxide), ZrO2 (zirconium oxide), and MnO (manganese oxide). This composite material approach allows the synergistic effects of different components to simultaneously improve reliability and maintain flat temperature characteristics, overcoming the limitation of single-component or simple two-component systems.
2Reliability
If a DC current having field strength of about 20 V/μm is applied at about 175° C., then the reliability requirement is met, but the existing dielectric ceramic composition cannot maintain adequate performance
Solution Approach 1:
The patent modifies the dielectric ceramic composition parameters by adding ZrO2 and optimizing the content ranges of other components to specifically enhance performance under high DC current field strength at elevated temperatures. The composition formula 100(Ba1-xCax)TiO3+aR2O3+bV2O5+cZrO2+dMnO with specified parameter ranges (0.03≦x≦0.20, 0.05≦a≦3.50, 0.22≦b≦2.50, 0.05≦c≦3.0, 0.01≦d≦0.30) is designed to maintain electrical stability under severe high-temperature loading conditions with DC field strengths of about 20 V/μm.
Solution Approach 2:
The composite dielectric ceramic material combines multiple oxide components with complementary properties: (Ba1-xCax)TiO3 provides high dielectric constant, R2O3 improves temperature stability, V2O5 enhances reliability, ZrO2 contributes to flat temperature-dependent change rate and structural stability, and MnO refines grain structure. This composite system collectively achieves the required reliability under high DC current field strength at 175°C while maintaining performance stability.
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 higher reliability and a smaller temperature-dependent change rate, ensuring excellent life characteristics even under severe high-temperature loading conditions, with additional benefits from the inclusion of SiO2 and MgO, allowing the use of conductive materials like Ni and Cu for electrodes without becoming semiconductor.
Implementation Method 1
the dielectric ceramic layers are made of a sintered compact of the dielectric ceramic composition according to the preferred embodiment of the present invention
Data Source
AI summary
Provided are a dielectric ceramic composition suitable for use in a monolithic ceramic capacitor that is employed in high-temperature environments such cars, and a monolithic ceramic capacitor constituted by using the dielectric ceramic composition. The dielectric ceramic composition has a composition formula of 100(Ba1-xCax)TiO3+aR2O3+bV2O5+cZrO2+dMnO (where R is at least one metal element selected from among Y, La, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb, and a, b, c and d denote values in terms of moles), and conditions of 0.03≦x≦0.20, 0.05≦a≦3.50, 0.22≦b≦2.50, 0.05≦c≦3.0, and 0.01≦d≦0.30 are substantially satisfied. The dielectric ceramic layers in the monolithic ceramic capacitor are made of a sintered compact of the dielectric ceramic composition.