SrTiO3 Dielectric Ceramic Composition for Capacitor Miniaturization

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Solution Overview

Problem

SrTiO3 dielectric ceramics have low dielectric constants, making it difficult to reduce the size of capacitors and are not suitable for laminated ceramic capacitors with base metal internal electrodes due to low resistance to reduction, and adding PbTiO3 and Bi2O3 increases dielectric constant but decreases resistance further.

Innovation Solution

A dielectric ceramic composition of (Sr1-x-ySnxBay)TiO3 with x between 0.005 and 0.24, and y between 0 and 0.25, including 0.01 to 5 mol of M (Mn or V) and 0.2 to 5 mol of SiO2, and 0.1 to 25 mol of CaO, which allows Sn to act as a bivalent cation at the A site, improving dielectric constant and enabling simultaneous calcination of dielectric ceramic layers and internal electrodes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Shape

If PbTiO3 and Bi2O3 are added to SrTiO3 dielectric ceramic to increase the dielectric constant, then the dielectric constant is improved, but the resistance to reduction deteriorates

Engineering Contradiction:

Improvedielectric constantVSAvoidresistance to reduction

Core Design Contradiction:

ShapeVSReliability

Solution Approach 1:

The patent changes the chemical composition parameters by substituting Sr with Sn and Ba in specific proportions (0.005≦x≦0.24 and 0≦y≦0.25 in the formula Sr1-x-ySnxBayTiO3). This parameter optimization allows achieving high dielectric constant (≥300) while maintaining resistance to reduction, resolving the contradiction between improving dielectric constant and maintaining reliability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite dielectric ceramic system combining SrTiO3 with controlled amounts of Sn and Ba substitutions, along with multiple additives (MnO, VO, SiO2, CaO) in specific ranges. This composite approach achieves both high dielectric constant and maintained resistance to reduction, unlike simple PbTiO3/Bi2O3 additions.

Inventive Principle:

Principle #40Composite materials

2Strength

If SnO2 is added to SrTiO3 dielectric ceramic to improve withstand voltage, then the withstand voltage is improved, but the dielectric constant decreases

Engineering Contradiction:

Improvewithstand voltageVSAvoiddielectric constant

Core Design Contradiction:

StrengthVSShape

Solution Approach 1:

The patent optimizes the Sn content parameter (x value) within a specific range (0.005≦x≦0.24) rather than simply increasing SnO2 addition. This controlled parameter change, combined with Ba substitution and additive optimization, simultaneously improves withstand voltage and maintains high dielectric constant, resolving the contradiction between strength and dielectric properties.

Inventive Principle:

Principle #35Parameter changes

3Volume of moving object

If the dielectric constant of SrTiO3 dielectric ceramic is increased, then the capacitor size can be reduced, but the resistance to reduction decreases when using base metal internal electrodes

Engineering Contradiction:

Improvecapacitor sizeVSAvoidresistance to reduction

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent optimizes multiple composition parameters simultaneously (Sr substitution with Sn and Ba, additive ratios of MnO, VO, SiO2, CaO) to achieve high dielectric constant (≥300) while maintaining resistance to reduction. This enables miniaturization with base metal internal electrodes, resolving the contradiction between volume reduction and reliability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent enables the use of base metal internal electrodes (cheaper materials) by maintaining resistance to reduction through optimized composition, allowing cost-effective capacitor miniaturization without sacrificing performance.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 dielectric constant is increased, allowing for a reduction in capacitor size, improved temperature characteristics, and reduced costs by enabling the use of base metal internal electrodes, while maintaining insulation resistance.

Implementation Method 1

Sn is located as a bivalent cation at the A site in a perovskite structure compound represented by ABO3

Methodology Applied

Scientific EffectBivalent cation substitution at A site:

Implementation Method 2

a predetermined mount of Ba is further substituted for Sr at the A site of the SrTiO3 main component

Methodology Applied

Scientific EffectCation substitution at A site:

Implementation Method 3

the addition of a predetermined amount of M (M is at least one of Mn and V) or the addition of a predetermined amount of Si allows the calcination temperature to be decreased

Methodology Applied

Scientific EffectCalcination:

Data Source

PatentUS8248753B2Dielectric ceramic and laminated ceramic capacitor

Publication Date: 2012.08.21 MURATA MFG CO LTD

AI summary

A dielectric ceramic for use in dielectric ceramic layers has a main component represented by a composition formula of (Sr1-x-ySnxBay)TiO3, wherein x is 0.005≦x≦0.24, y is 0≦y≦0.25 in the composition formula. Preferably, the dielectric ceramic includes 0.01 mol to 5 mol of M (M is at least one of Mn and V) calculated as MO and/or 0.2 mol to 5 mol of Si calculated as SiO2, with respect to 100 mols of the main component, and more preferably, further includes 0.1 mol to 25 mol of Ca calculated as CaO with respect to 100 mols of the main component. The dielectric ceramic has an increased dielectric constant permitting size reduction when used in a laminated ceramic capacitor.