Dielectric Ceramic for Stable Capacitance at 150°C
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Solution Overview
Problem
Capacitors used in automobiles require even capacitance characteristics across a temperature range of −55° C. to 150° C., but existing dielectric ceramics have small specific resistance and large temperature coefficients of capacitance at 150° C.
Innovation Solution
A dielectric ceramic with perovskite type compounds containing Ba, Ca, Ti, Zr, and Si, optionally with Mn, having specific molar ratios and average grain sizes less than 130 nm, is used to enhance specific resistance and maintain even capacitance at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional dielectric ceramic is used, then the capacitor can be manufactured, but the specific resistance is small and the temperature coefficient of capacitance is large at 150° C.
Solution Approach 1:
The patent applies parameter changes by precisely controlling the molar ratios of Ba, Ca, Ti, and Zr in the perovskite compound, and by controlling the grain size within a specific range (50-130 nm). These parameter adjustments optimize the dielectric properties to achieve stable capacitance characteristics at high temperatures while maintaining high specific resistance.
Solution Approach 2:
The patent uses composite materials by combining multiple elements (Ba, Ca, Ti, Zr) in a perovskite structure to create a dielectric ceramic with superior properties. The composite nature of this material allows it to simultaneously achieve high specific resistance and stable capacitance characteristics at 150° C., resolving the contradiction between reliability and temperature sensitivity.
2Reliability
If conventional dielectric ceramic is used, then the capacitor can be manufactured, but the specific resistance is small at 150° C.
Solution Approach 1:
The patent achieves high specific resistance at 150° C. by changing the compositional parameters of the perovskite compound, specifically the molar ratios of Ba, Ca, Ti, and Zr, and by controlling the grain size to be within 50-130 nm. These parameter optimizations significantly improve the dielectric loss and specific resistance characteristics at elevated temperatures.
Solution Approach 2:
The use of a composite perovskite material containing Ba, Ca, Ti, and Zr in specific proportions creates a dielectric ceramic with enhanced electrical properties. This composite structure provides high specific resistance at 150° C. while maintaining good capacitance stability, effectively resolving the contradiction between reliability and high-temperature performance.
Data Source
AI summary
There are provided a dielectric ceramic having large specific resistance and even capacitance characteristic at 150° C., as well as a laminated ceramic electronic component employing such a dielectric ceramic. A ceramic layer includes crystal grains, the ceramic layer containing a perovskite type compound containing Ba, Ca, Ti, and Zr, containing Si, and optionally containing Mn. When the total content of Ti and Zr is 1 molar part, the content of Mn is 0.015 molar part or less, the content of Si is 0.005 molar part or more and less than 0.03 molar part, the molar ratio x of Ca/(Ba+Ca) satisfies 0.05<x<0.20, and the molar ratio y of Zr/(Ti+Zr) satisfies 0.03<y<0.18. The crystal grains have an average grain size of less than 130 nm.