Multi-layer Piezoelectric Element Voids Reduce Electrode Peeling
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Solution Overview
Problem
Conventional multi-layer piezoelectric elements experience electrode peeling off due to stress at joining interfaces under high electric fields and prolonged continuous driving, leading to deteriorated displacement characteristics.
Innovation Solution
A multi-layer piezoelectric element design featuring a stacked body with piezoelectric and internal electrode layers, where voids are formed in the joining interface between the external electrode and the stacked body, reducing stress through a flat void shape that is long in the planar direction, and optionally incorporating a glass layer for enhanced joining strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional conductive paste external electrodes are used and adhered to side faces of stacked body, then the multi-layer piezoelectric element can be manufactured with standard processes, but portions of the external electrodes peel off from the side faces during use under severe conditions such as high electric field, high pressure, or prolonged continuous driving
Solution Approach 1:
The invention introduces a porous coating layer on the external electrode surface that contains voids (air pockets) within its structure. These voids act as stress-absorbing elements that prevent stress concentration at the joining interface between the external electrode and the stacked body side face. The porous structure allows the coating layer to deform elastically under stress, preventing electrode peeling while maintaining electrical conductivity through the conductive paste matrix.
2Ease of operation
If the stacked body expands and contracts in the lamination direction by applying voltage, then the piezoelectric element functions as intended, but stress is generated in joining interfaces between the stacked body and external electrodes causing electrode peeling
Solution Approach 1:
The porous coating layer with embedded voids serves as a pre-configured cushioning structure at the joining interface. Before stress buildup causes electrode peeling, the voids are already in place to absorb and distribute the expansion/contraction stresses generated during piezoelectric actuation. This beforehand cushioning prevents the harmful stress concentration that would otherwise lead to interface failure.
3Duration of action of moving object
If continuous driving for prolonged period of time is required, then the piezoelectric element must maintain displacement characteristics, but repeated stress generation causes electrode peeling and displacement deterioration
Solution Approach 1:
The porous coating layer with stress-absorbing voids ensures continuous stress protection at the joining interface throughout prolonged operation. By preventing electrode peeling during each expansion-contraction cycle, the coating layer maintains the integrity of the electrical connection and displacement characteristics over extended periods of continuous driving, enabling reliable long-term operation.
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 voids effectively reduce stress at the joining interface, preventing electrode peeling and maintaining displacement characteristics over prolonged high-electric-field and high-pressure conditions, ensuring stable operation of the piezoelectric element.
Implementation Method 1
a stacked body in which piezoelectric layers and internal electrode layers are alternately laminated
Data Source
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AI summary
Provided is a highly durable multi-layer piezoelectric element wherein an external electrode has less possibilities of being peeled off from a side face of a stacked body even when the element is continuously driven for a long period of time in a high electrical field under high pressure. In a multi-layer piezoelectric element (1), a void (2) is formed in a joining interface between a side face of a stacked body (7) wherein piezoelectric layers (3) and internal electrode layers (5) are alternately laminated and an external electrode (9) joined to the side face. Since stress generated in the joining interface between the side face of the stacked body (7) and the external electrode (9) during driving can be reduced by the void (2), there are less possibilities of having the external electrode (9) peeled off from the side face of the stacked body (7) even when the element is continuously driven for a long period of time.