Piezoelectric Multilayer Component with Controlled Crack Propagation
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Solution Overview
Problem
Piezoelectric multilayer components face instability under mechanical loads, leading to premature failure due to uncontrolled cracking and short circuits, which affects their operational longevity.
Innovation Solution
A piezoelectric multilayer component is designed with a stack of green piezoceramic layers and electrode layers where copper is used as the primary metal, diffusing from a higher concentration layer to a lower concentration layer, creating cavities that act as a predetermined breaking layer, thereby controlling crack propagation parallel to the layers and maintaining electrical connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrode layers with uniform metal distribution are used, then the component maintains structural integrity, but it suffers from uncontrolled cracking and premature failure under mechanical loads
Solution Approach 1:
The electrode layers are designed with non-uniform metal concentration distribution, creating regions of different mechanical properties within the same layer. The second electrode layer has higher metal concentration in specific areas to create predetermined breaking zones, while other areas maintain lower concentration for structural support. This local variation in composition allows the component to control crack propagation paths and prevent catastrophic failure.
2Reliability
If the metal concentration difference between electrode layers is increased to create predetermined breaking layers, then controlled cracking is achieved, but the electrical conductivity of the electrode layers deteriorates
Solution Approach 1:
The invention carefully controls the metal concentration parameter within optimized ranges. The second electrode layer contains 60-90 wt% metal (optimal 70-80 wt%) in breaking zones and 30-60 wt% (optimal 40-50 wt%) in support zones. The first electrode layer contains 30-60 wt% (optimal 40-50 wt%) metal. These parameter ranges ensure sufficient electrical conductivity while maintaining the predetermined breaking layer functionality.
3Temperature
If copper is used as the primary metal for gentle sintering, then the sintering temperature can be reduced, but copper diffuses more easily through piezoceramic layers compared to other metals
Solution Approach 1:
The non-uniform metal concentration distribution is established in the green state (before sintering) through selective application or deposition techniques. This preliminary configuration ensures that during sintering, even though copper diffuses more readily, the overall concentration gradient and breaking layer structure are maintained because the initial distribution was deliberately designed to account for expected diffusion behavior.
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 enhances mechanical stability and operational longevity by ensuring controlled cracking and maintaining electrical functionality, preventing short circuits and ensuring the component remains electrically active during operation.
Implementation Method 1
the first metal diffuses from the second electrode layer partially to the first electrode layer and leaves cavities in the second electrode layer
Implementation Method 2
If the intermediate product is sintered, the first metal diffuses from the second electrode layer partially to the first electrode layer
Data Source
Figure 1~3
Figure 4~5
AI summary
A piezoelectric multilayer component as intermediate product is disclosed, comprising a stack (1) of superimposed green piezoceramic layers (2), wherein a first electrode layer (3a) is applied to a piezoceramic layer (2) and contains a first metal. A second electrode layer (3b) is applied to a further piezoceramic layer (2) adjacent to the first electrode layer (3a) in the direction of stacking. The second electrode layer (3b) contains the first metal in a higher concentration than the first electrode layer (3a). The invention further relates to a method for producing a piezoelectric multilayer component, wherein the intermediate product is sintered and the first metal diffuses from the second electrode layer (3b) to the first electrode layer (3a) thus mechanically weakening the second electrode layer (3b).