High Temperature Ceramic Dielectric Composition for 300°C Capacitors
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Solution Overview
Problem
Conventional multilayer ceramic capacitors based on modified barium titanate lose significant dielectric constant at high temperatures, limiting their capacitance and reliability in operating ranges of 150° C. to 300° C., which is critical for high-temperature power electronics applications.
Innovation Solution
A high-temperature ceramic dielectric composition is developed by doping a base Mex(Bi0.5Na0.5)1-xTiO3 with donor ions like Nb5+, Nd3+, Zn2+, and Mn2+, along with a glass forming agent such as SiO2, forming a heterogeneous core/shell structure that maintains a high dielectric constant and reduces losses across the temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional BaTiO3 based dielectrics are used to meet electronic industry standards (X7R, X8R, BX), then the capacitors can operate reliably up to 150°C, but the dielectric constant decreases by 45% or more at 200°C, severely limiting capacitance in higher temperature ranges
Solution Approach 1:
The patent employs a composite dielectric system consisting of a BaTiO3 core surrounded by a heavily doped shell region containing donor/acceptor dopants and fluxing additions. This core/shell composite structure allows the inner core to provide high dielectric constant while the outer shell maintains stability and suppresses phase transitions, achieving both high reliability and maintained capacitance at temperatures up to 300°C
Solution Approach 2:
The dielectric exhibits spatially varying properties through the core/shell structure: the core region has high dielectric constant for capacitance, while the shell region has modified composition with dopants and fluxes for thermal stability. This local differentiation of material properties enables simultaneous optimization of both dielectric constant and temperature stability
2Adaptability or versatility
If the operating temperature range is extended from 150°C to 300°C, then high temperature power electronics applications become enabled, but conventional dielectrics lose most of their dielectric constant, requiring larger capacitor sizes to achieve the same capacitance
Solution Approach 1:
The core/shell composite dielectric structure enables extended temperature adaptability by combining BaTiO3 core with a stabilizing shell containing dopants and fluxes, maintaining dielectric constant at temperatures up to 300°C and enabling high temperature power electronics applications without requiring larger capacitor volumes
3Ease of manufacture
If donor/acceptor dopants and fluxing additions are added to shift and flatten the Curie point, then the sintering characteristics improve and electronic industry temperature coefficients are met, but the heterogeneous core/shell structure causes significant dielectric constant loss at high temperatures
Solution Approach 1:
The patent localizes the dopant and flux effects to the shell region surrounding the BaTiO3 core. This spatial distribution allows the shell to provide sintering enhancement and temperature coefficient control through heavy doping, while the undoped or lightly-doped core maintains high dielectric constant, thereby resolving the contradiction between manufacturability and dielectric performance
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 new composition achieves a dielectric constant of 3600 to 4000 or greater with less than 1% loss, maintaining stability and capacitance over 150° C. to 300° C., offering 10 times the capacitance of traditional capacitors or allowing for size reduction, while being environmentally friendly by avoiding lead, cadmium, and hexavalent chromium.
Implementation Method 1
The applicable dielectric ceramic is produced by doping a base Mex(Bi0.5Na0.5)1-xTiO3 composition with donors such as Nb5+ and Nd3+, acceptors such as Zn2+ and Mn2+, and a glass forming agent such as SiO2
Implementation Method 2
the addition of the dopants Nb5+, Nd3+, Zn2+, and Mn2+, along with addition of the glass forming agent forms a heterogeneous 'core/shell' type structure when sintered to high densification
Implementation Method 3
The new composition achieves a dielectric constant of 3600 to 4000 or greater with less than 1% loss, maintaining stability and capacitance over 150° C. to 300° C.
Data Source
AI summary
A bismuth sodium titanate (Bi0.5Na0.5TiO3) base material is modified by the partial substitution of aliovalent A-site cations such as barium (as BaO) or strontium (as SrO), as well as certain b-site donor/acceptor dopants and sintering aids to form a multi-phase system, much like known “core/shell” X7R dielectrics based solely on BaTiO3. The resulting ceramic dielectric composition is particularly suitable for producing a multilayer ceramic capacitor (10) that maintains high dielectric constant (and thus the capability of maintaining high capacitance) over a broad temperature range of from about 150° C. to about 300° C. Such capacitors (10) are appropriate for high temperature power electronics applications in fields such as down-hole oil and gas well drilling.