Li-Free Dielectric Ceramic Composition for High-Temperature MLCCs
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Solution Overview
Problem
Current dielectric ceramic materials, such as BaTiO3, face limitations in maintaining stable capacitance at high temperatures, especially above 150°C, due to ferroelectric-to-paraelectric phase transitions and high leakage currents caused by light elements like Li, which are detrimental in harsh environments.
Innovation Solution
A dielectric ceramic composition comprising [(Na1-xKx)sA1-s](Nb1-yTay)uB1vB2w)O3, where A is an alkaline-earth element, B1 is Ti, Zr, or Sn, and B2 is a transition metal, with rare-earth elements and a Li-free frit, enabling co-firing with base metals like Ni at low oxygen partial pressures, resulting in multilayer ceramic capacitors with stable temperature-capacitance characteristics up to 200°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If Li is added to alkaline niobate-based ceramics to improve sintering and co-firing characteristics, then ease of manufacture is improved, but leakage current increases significantly in harsh environments
Solution Approach 1:
The patent removes Li from the ceramic composition entirely, extracting the harmful element that causes high leakage current while retaining other beneficial components like alkaline-earth elements and transition metals that provide sintering assistance and co-firing compatibility
Solution Approach 2:
The patent replaces Li with alternative dopants that provide temporary or localized functionality during manufacturing (sintering and co-firing) without persisting as harmful elements in the final product, effectively using substitute materials that serve their purpose and then cease to be problematic
2Reliability
If BaTiO3 is used as dielectric material to achieve high dielectric constant and low loss, then electrical performance is improved, but temperature stability deteriorates above 125°C due to phase transition
Solution Approach 1:
The patent employs composite material strategy by combining alkaline niobate-based ceramics with alkaline-earth zirconates/hafnates and transition metal dopants, creating a multi-component system where each element contributes specific properties: alkaline-earth elements provide high dielectric constant, zirconates/hafnates enhance temperature stability, and transition metals suppress phase transitions, collectively achieving both electrical performance and temperature stability
Solution Approach 2:
The patent changes the chemical composition parameters of the dielectric material by substituting BaTiO3 with alkaline niobate-based ceramics doped with specific ratios of alkaline-earth elements (Ca, Sr, Ba) and transition metals (V, Cr, Mn, Fe, Co, Ni, Cu, Zn), thereby shifting the phase transition temperature and stabilizing capacitance across the extended temperature range of -55°C to 200°C
3Ease of manufacture
If alkaline niobate-based ceramics are used to enable co-firing with base metals at low oxygen partial pressure, then ease of manufacture is improved, but dielectric stability deteriorates due to high leakage current
Solution Approach 1:
The patent extracts Li from the composition to eliminate the source of high leakage current and dielectric instability, while preserving the alkaline niobate-based ceramic framework that enables co-firing with base metals at low oxygen partial pressure
Solution Approach 2:
The patent introduces alkaline-earth elements (Ca, Sr, Ba) and transition metal dopants as intermediary substances that mediate between the alkaline niobate matrix and base metal electrodes, providing both sintering assistance for co-firing compatibility and suppression of leakage current to maintain dielectric 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 solution provides multilayer ceramic capacitors with a temperature coefficient of capacitance within ±25% from -55°C to 200°C, maintaining dielectric stability and reducing leakage currents, thus addressing the limitations of existing materials in high-temperature applications.
Implementation Method 1
enabling co-firing with base metals like Ni at low oxygen partial pressures
Implementation Method 2
BaTiO3 has been well known as a ferroelectric material which experiences a ferroelectric-to-paraelectric phase transition around 125° C.
Data Source
AI summary
The present invention discloses a dielectric ceramic formula enabling one to obtain a multilayer ceramic capacitor by alternatively stacking the ceramic dielectric layers and base metal internal electrodes. The dielectric ceramic composition comprises a primary ingredient:[(Na1-xKx)sA1-s]m[(Nb1-yTay)uB1vB2w)]O3 wherein:A, B1, B2, x, y, s, u, v, w and m are defined.