Piezoelectric Surface Electrode Adhesion via Silver Palladium Alloy
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Solution Overview
Problem
Piezoelectric elements experience instability and surface electrode peeling due to stress, leading to unreliable long-term operation in piezoelectric vibrating devices, portable terminals, acoustic generators, and electronic apparatuses.
Innovation Solution
A piezoelectric element with a surface electrode comprising a first area mainly containing silver and a second area mainly containing silver palladium, which is electrically connected to inner electrodes and contacts the piezoelectric layer, enhancing adhesion and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a baked Ag electrode is used with uniform thickness and surface condition over the entire region, then the piezoelectric element can be driven uniformly across the entire surface region, but microcracks may be generated at the interface between the surface electrode and piezoelectric layer under stress, leading to peeling and unstable displacement
Solution Approach 1:
The surface electrode is designed with different material compositions in different regions: a first region containing silver and a second region containing silver palladium alloy. This local differentiation allows the electrode to have optimized properties in each region - the silver region provides good electrical conductivity for uniform driving, while the silver palladium region provides enhanced adhesion to prevent peeling under stress.
Solution Approach 2:
The surface electrode uses a composite structure combining two different materials: pure silver (or silver-rich) and silver palladium alloy. This composite approach leverages the advantages of both materials - the high conductivity of silver and the superior adhesion properties of silver palladium - to simultaneously achieve uniform driving and reliable electrode attachment.
2Duration of action of moving object
If the surface electrode is driven for a long period of time under stress, then the piezoelectric element can maintain continuous operation, but the surface electrode may peel off due to microcrack generation, resulting in unstable displacement amount
Solution Approach 1:
The silver palladium region is positioned at the interface with the piezoelectric layer to preemptively counteract the peeling force that develops during long-term operation. This preventive design cushions against the harmful effects of stress accumulation and microcrack formation, ensuring continuous stable operation without displacement instability.
3Reliability
If the surface electrode is peeled off, then the piezoelectric vibrating device cannot be stably driven for a long period of time, but using a uniform Ag electrode structure increases the risk of peeling under long-term stress
Solution Approach 1:
Rather than making the entire electrode complex, only specific regions are differentiated. The silver palladium alloy is applied selectively in the second region where adhesion is critical, while the first region maintains simple silver composition for optimal conductivity. This localized complexity achieves reliability without excessive overall device complexity.
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 effectively suppresses surface electrode peeling and stabilizes displacement over time, ensuring stable long-term operation of piezoelectric devices and apparatuses by improving the adhesion and uniform voltage application across the surface electrode.
Implementation Method 1
A piezoelectric element includes a plate-shaped stacked body including inner electrodes and piezoelectric layers laminated
Implementation Method 2
a second area mainly containing silver palladium and disposed so as to contact a piezoelectric layer
Data Source
AI summary
There are provided a piezoelectric element in which the peeling of a surface electrode is suppressed, and a piezoelectric vibrating device, a portable terminal, an acoustic generator, an acoustic generating device and an electronic apparatus including the same. A piezoelectric actuator includes a piezoelectric element including a plate-shaped stacked body including inner electrodes and piezoelectric layers laminated, a surface electrode disposed on one of main surfaces of the stacked body, the surface electrode being electrically connected to the inner electrodes. The surface electrode has a first area and a second area. The first area is an area mainly containing silver, and the second area is an area mainly containing silver and palladium and disposed so as to contact a piezoelectric layer.