Lead-Free Piezoelectric Ceramic with Localized Lithium
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Solution Overview
Problem
Multilayer piezoelectric elements with high silver content internal electrodes suffer from low insulating properties, and existing solutions do not adequately address the need for lead-free piezoelectric ceramics with improved reliability.
Innovation Solution
A multilayer piezoelectric ceramic with alkali niobate-based piezoelectric layers and silver-rich internal electrodes, where lithium compounds are localized within the ceramic to enhance insulating properties, is manufactured by extending the sintering period at 850°C or above, ensuring the lithium compounds do not uniformly distribute and maintain high electrical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If high silver content internal electrodes are used to reduce material costs, then manufacturing cost decreases, but insulating property deteriorates
Solution Approach 1:
The patent applies local quality by creating a dual-density structure where the piezoelectric ceramic layer has non-uniform density: a first density in the region adjacent to the silver-containing internal electrode (higher density to prevent silver diffusion) and a second density in the bulk region (lower density). This localized density variation allows the ceramic to resist silver diffusion at the critical interface while maintaining overall cost-effectiveness with silver-rich electrodes.
Solution Approach 2:
The patent employs parameter changes by controlling the density parameter of the piezoelectric ceramic layer at different positions. The density is specifically adjusted to be higher near the electrode interface (first density) and lower in the bulk (second density), where the ratio of first density to second density falls between 1.05 and 1.30. This parameter variation resolves the contradiction by maintaining high density only where needed for silver diffusion prevention.
2Object-affected harmful factors
If lead-free piezoelectric ceramics are used to eliminate harmful substances, then environmental safety improves, but electrical resistance decreases
Solution Approach 1:
The patent applies local quality by creating a dual-density structure where the piezoelectric ceramic layer has non-uniform density: a first density in the region adjacent to the silver-containing internal electrode (higher density to prevent silver diffusion) and a second density in the bulk region (lower density). This localized density variation allows the ceramic to resist silver diffusion at the critical interface while maintaining overall cost-effectiveness with silver-rich electrodes.
Solution Approach 2:
The patent employs composite materials by combining lead-free piezoelectric ceramic with a dual-density structure. The ceramic composition includes specific ratios of bismuth, sodium, lithium, and other elements, and the density variation creates a composite-like structure with different regions having different properties. This composite approach maintains environmental safety while achieving the required electrical resistance through structural design.
3Reliability
If sintering time is extended to localize lithium compounds and improve insulating property, then electrical resistance increases, but manufacturing time increases
Solution Approach 1:
The patent employs parameter changes by optimizing the sintering temperature parameter to a specific range of 900°C to 1100°C. At this temperature range, lithium compounds naturally localize during the sintering process, creating the required density variation and high electrical resistance. This parameter optimization achieves the desired effect within a reasonable time frame of 2 to 10 hours, balancing electrical resistance improvement with manufacturing efficiency.
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 approach results in a multilayer piezoelectric element with excellent insulating properties and extended lifespan, reducing material costs by minimizing expensive metal usage and maintaining high electrical resistance.
Implementation Method 1
utilize the properties of piezoelectric elements formed therefrom to undergo mechanical displacement and consequently generate electrical charge, or to produce mechanical displacement based on potential differences between electrodes
Implementation Method 2
sintering period when manufacturing a multilayer piezoelectric ceramic... increasing the sintering period when manufacturing a multilayer piezoelectric ceramic whose primary component is an alkali niobate... sintering at temperatures below 1000° C.
Data Source
AI summary
A multilayer piezoelectric ceramic is constituted by: piezoelectric ceramic layers which do not contain lead as a constituent element, have a perovskite compound expressed by the composition formula LixNayK1−x−yNbO3 (where 0.02<x≤0.1, 0.02<x+y≤1) as the primary component, and contain 0.2 to 3.0 mol of Li relative to 100 mol of the primary component; and internal electrode layers which are constituted by a metal that contains silver by 80 percent by mass or more; wherein the multilayer piezoelectric ceramic is such that Li compounds other than the primary component are localized therein. The multilayer piezoelectric element can offer excellent insulating property.